| 1. |
- Setala, T., et al.
(författare)
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Complete electromagnetic coherence in the space-frequency domain
- 2004
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 29:4, s. 328-330
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Tidskriftsartikel (refereegranskat)abstract
- We show that the following properties of a random electromagnetic field are equivalent: (i) the field is spatially completely coherent in the sense of the recently introduced electromagnetic degree of coherence and (ii) the electric cross-spectral density tensor factors in the two spatial variables.
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| 2. |
- Abdullaev, Farakhulla, et al.
(författare)
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Zeno effect and switching of solitons in nonlinear couplers
- 2011
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Ingår i: Optics Letters. - : Optical Society of America. - 0146-9592 .- 1539-4794. ; 36:23, s. 4566-4568
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Tidskriftsartikel (refereegranskat)abstract
- The Zeno effect is investigated for soliton type pulses in a nonlinear directional coupler with dissipation. The effect consists in increase of the coupler transparency with increase of the dissipative losses in one of the arms. It is shown that localized dissipation can lead to switching of solitons between the arms. Power losses accompanying the switching can be fully compensated by using a combination of dissipative and active (in particular, parity-time-symmetric) segments.
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| 3. |
- Albert, Jacques, et al.
(författare)
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Grating formation in pure silica-core fibers
- 2002
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 27:10, s. 809-811
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Tidskriftsartikel (refereegranskat)abstract
- Strong grating formation in pure silica-core fibers by use of 193-nm ArF-laser radiation is reported. Unsaturated refractive-index changes of Deltan similar to 0.3 X 10(-3) were observed in nontreated fiber, and changes of Deltan similar to 0.5 X 10(-3) were observed in fibers with a high hydroxyl concentration. Possible mechanisms of photosensitivity in pure silica-core fibers are discussed.
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| 4. |
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| 5. |
- Alessi, D, et al.
(författare)
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Gain-saturated 10.9 nm tabletop laser operating at 1 Hz repetition rate
- 2010
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Ingår i: Optics Letters. - : Optical Society of America. - 0146-9592 .- 1539-4794. ; 35:3, s. 414-6
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Tidskriftsartikel (refereegranskat)abstract
- We report the demonstration of a gain-saturated 10.9 nm tabletop soft x-ray laser operating at 1 Hz repetition rate. Lasing occurs by collisional electron impact excitation in the 4dS01-->4pP11 transition of nickel-like Te in a line-focus plasma heated by a chirped-pulse-amplification Ti:sapphire laser. With an average power of 1muW and pulse energy up to approximately 2microJ, this laser extends the ability to conduct tabletop laser experiments to a shorter wavelength.
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| 6. |
- Anders, Berntson, et al.
(författare)
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Dispersion management with filtering
- 1999
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Ingår i: Optics Letters. - : Optical Society of America Inc.. - 0146-9592 .- 1539-4794. ; 24:8, s. 507-509
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Tidskriftsartikel (refereegranskat)abstract
- With regards to their potential to improving the pulse-based regimes in optical communication networks, dispersion-managed solitons in a fiber link including guiding filters and compensating gain were investigated. Combining the variational approximation and the perturbative treatment of the filtering and gain, stationary regimes are predicted. Among other features, the minimum map strength necessary for the existence of the pulses when path-averaged dispersion (PAD) is zero or normal is absent, rather, a minimum necessary normalized power for any PAD exists.
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| 7. |
- Anders, Berntson, et al.
(författare)
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Power dependence of dispersion-managed solitons for anomalous, zero, and normal path-average dispersion
- 1998
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Ingår i: Optics Letters. - Goteborg, Sweden : Chalmers Tekniska Hogskola. - 0146-9592 .- 1539-4794. ; 23:12, s. 900-902
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- We determine the power dependence of dispersion-managed solitons on map strength and average dispersion, using a combination of numerical simulations and the variational approach. In particular, we investigate the behavior near zero dispersion and identify the region of existence of dispersion-managed solitons in the average normal-dispersion regime.
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| 8. |
- Andersen, Torben, et al.
(författare)
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Neural networks for image-based wavefront sensing for astronomy
- 2019
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Ingår i: Optics Letters. - : Optical Society of America. - 0146-9592 .- 1539-4794. ; 44:18, s. 4618-4621
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Tidskriftsartikel (refereegranskat)abstract
- We study the possibility of using convolutional neural networks for wavefront sensing from a guide star image in astronomical telescopes. We generated a large number of artificial atmospheric wavefront screens and determined associated best-fit Zernike polynomials. We also generated in-focus and out-of-focus point-spread functions. We trained the well-known “Inception” network using the artificial data sets and found that although the accuracy does not permit diffraction-limited correction, the potential improvement in the residual phase error is promising for a telescope in the 2–4 m class.
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| 9. |
- Ansari, Nazanin, et al.
(författare)
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Multicolor filter all-garnet magneto-optical photonic crystals
- 2012
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 37:17, s. 3552-3554
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a multicolor optical filter and isolator based on a double-cavity magneto-optical (MO) photonic crystal. Being grown as a heteroepitaxial all-garnet multilayer, it compromises a strong MO response and high optical transmittance. Low-loss, high Faraday rotation passbands as well as strong light rejection within the stop band were achieved by optimization of distance between cavities and repetition number of distributed Bragg reflectors.
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| 10. |
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| 11. |
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| 12. |
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| 13. |
- Arabi, C. Mas, et al.
(författare)
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Localized structures formed through domain wall locking in cavity-enhanced second-harmonic generation
- 2020
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Ingår i: Optics Letters. - : OPTICAL SOC AMER. - 0146-9592 .- 1539-4794. ; 45:20, s. 5856-5859
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Tidskriftsartikel (refereegranskat)abstract
- We analyze the formation of localized structures in cavity-enhanced second-harmonic generation. We focus on the phase-matched limit, and consider that fundamental and generated waves have opposite signs of group velocity dispersion. We show that these states form due to the locking of domain walls connecting two stable homogeneous states of the system, and undergo collapsed snaking. We study the impact of temporal walk-off on the stability and dynamics of these localized states. (C) 2020 Optical Society of America
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| 14. |
- Arwin, Hans, et al.
(författare)
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Structural circular birefringence and dichroism quantified by differential decomposition of spectroscopic transmission Mueller matrices from Cetonia aurata
- 2016
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Ingår i: Optics Letters. - : OPTICAL SOC AMER. - 0146-9592 .- 1539-4794. ; 41:14, s. 3293-3296
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Tidskriftsartikel (refereegranskat)abstract
- Transmission Mueller-matrix spectroscopic ellipsometry is applied to the cuticle of the beetle Cetonia aurata in the spectral range 300-1000 nm. The cuticle is optically reciprocal and exhibits circular Bragg filter features for green light. By using differential decomposition of the Mueller matrix, the circular and linear birefringence as well as dichroism of the beetle cuticle are quantified. A maximum value of structural optical activity of 560 degrees/mm is found. (C) 2016 Optical Society of America
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| 15. |
- Balliu, Enkeleda, PhD student, et al.
(författare)
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High-efficiency radiation-balanced Yb-doped silica fiber laser with 200-mW output
- 2024
-
Ingår i: Optics Letters. - : Optica Publishing Group. - 0146-9592 .- 1539-4794. ; 49:8, s. 2021-2024
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Tidskriftsartikel (refereegranskat)abstract
- The focus of this study was the development of a second generation of fiber lasers internally cooled by anti-Stokes fluorescence. The laser consisted of a length of a single-mode fiber spliced to fiber Bragg gratings to form the optical resonator. The fiber was single-moded at the pump (1040 nm) and signal (1064 nm) wavelengths. Its core was heavily doped with Yb, in the initial form of CaF2 nanoparticles, and co-doped with Al to reduce quenching and improve the cooling efficiency. After optimizing the fiber length (4.1 m) and output-coupler reflectivity (3.3%), the fiber laser exhibited a threshold of 160 mW, an optical efficiency of 56.8%, and a radiation-balanced output power (no net heat generation) of 192 mW. On all three metrics, this performance is significantly better than the only previously reported radiation-balanced fiber laser, which is even more meaningful given that the small size of the single-mode fiber core (7.8-µm diameter). At the maximum output power (∼2 W), the average fiber temperature was still barely above room temperature (428 mK). This work demonstrates that with anti-Stokes pumping, it is possible to induce significant gain and energy storage in a small-core Yb-doped fiber while keeping the fiber cool.
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| 16. |
- Barrios, Carlos Angulo, et al.
(författare)
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Label-free optical biosensing with slot-waveguides
- 2008
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 33:7, s. 708-710
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate label-free molecule detection by using an integrated biosensor based on a Si3N4/SiO2 Slot-waveguide microring resonator. Bovine serum albumin (BSA) and anti-BSA molecular binding events on the sensor surface are monitored through the measurement of resonant wavelength shifts with varying biomolecule concentrations. The biosensor exhibited sensitivities of 1.8 and 3.2 nm/(ng/mm(2)) for the detection of anti-BSA and BSA, respectively. The estimated detection limits are 28 and 16 pg/mm(2) for anti-BSA and BSA, respectively, limited by wavelength resolution.
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| 17. |
- Barrios, Carlos Angulo, et al.
(författare)
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Slot-waveguide biochemical sensor
- 2007
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 32:21, s. 3080-3082
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Tidskriftsartikel (refereegranskat)abstract
- We report an experimental demonstration of an integrated biochemical sensor based on a slot-waveguidemicroring resonator. The microresonator is fabricated on a Si3N4-SiO2 platform and operates at a wavelength of 1.3 mu m. The transmission spectrum of the sensor is measured with different ambient refractive indices ranging from n = 1. 33 to 1.42. A linear shift of the resonant wavelength with increasing ambient refractive index of 212 nm/refractive index units (RIU) is observed. The sensor detects a minimal refractive index variation of 2 X 10(-4) RIU.
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| 18. |
- Barrios, Carlos A., et al.
(författare)
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Slot-waveguide biochemical sensor (vol 32, pg 2080, 2007)
- 2008
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Ingår i: Optics Letters. - : OPTICAL SOC AMER. - 0146-9592 .- 1539-4794. ; 33:21, s. 2554-2555
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Tidskriftsartikel (refereegranskat)abstract
- The group index, instead of the effective index, is used to analyze the performance of a Si(3)N(4)-SiO(2) slot-waveguide microring refractive index sensor [Opt. Lett. 32, 3080 (2007)]. Assuming that the slot is fully filled with liquid, excellent agreement is found between experimental results and calculations.
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| 19. |
- Berrill, Mark, et al.
(författare)
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Improved beam characteristics of solid-target son x-ray laser amplifiers by injection seeding with high harmonic pulses
- 2010
-
Ingår i: Optics Letters. - : Optical Society of America. - 0146-9592 .- 1539-4794. ; 35:14, s. 2317-2319
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Tidskriftsartikel (refereegranskat)abstract
- Injection seeding of solid-target soft x-ray laser amplifiers with high harmonic pulses is shown to dramatically improve the far-field laser beam profile and reduce the beam divergence. Measurements and two-dimensional simulations for a 13.9 nm nickel-like Ag amplifier show that the amplified beam divergence depends strongly on the seed and can therefore be controlled by selecting the divergence of the seed. The near-field beam size of both the seeded and unseeded lasers is shown to be determined by the size of the gain region and the divergence of the amplified beams.
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| 20. |
- Bertilson, Michael, et al.
(författare)
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Laboratory soft-x-ray microscope for cryotomography of biological specimens
- 2011
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 36:14, s. 2728-2730
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Tidskriftsartikel (refereegranskat)abstract
- Soft-x-ray cryotomography allows quantitative and high-resolution three-dimensional imaging of intact unstained cells. To date, the method relies on synchrotron-radiation sources, which limits accessibility for researchers. Here we present a laboratory water-window microscope for cryotomography. It is based on a lambda = 2.48nm liquid-jet laser-plasma source, a normal-incidence multilayer condenser, a 30nm zone-plate objective, and a cryotilt sample holder. We demonstrate high-resolution imaging, as well as quantitative tomographic imaging, of frozen intact cells. The reconstructed tomogram of the intracellular local absorption coefficient shows details down to similar to 100nm.
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| 21. |
- Boyko, Andrey A., et al.
(författare)
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Rb:PPKTP optical parametric oscillator with intracavity difference-frequency generation in AgGaSe2
- 2016
-
Ingår i: Optics Letters. - : Optical Society of America. - 0146-9592 .- 1539-4794. ; 41:12, s. 2791-2794
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Tidskriftsartikel (refereegranskat)abstract
- A 1.064 mu m pumped Rb:PPKTP optical parametric oscillator (OPO) generates mid-IR radiation by intracavity mixing the resonant signal and idler waves in AgGaSe2. The similar to 6 ns pulses at similar to 7 mu m have an energy of 670 mu J at 100 Hz, equivalent to an average power of 67 mW. The overall quantum conversion efficiency from 1.064 mu m amounts to 8%, and the power conversion efficiency is 1.2%.
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| 22. |
- Bratfalean, Radu, et al.
(författare)
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Harmonic generation in a two-dimensional nonlinear quasi-crystal
- 2005
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 30:4, s. 424-426
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Tidskriftsartikel (refereegranskat)abstract
- Second-harmonic generation in a two-dimensional nonlinear quasi-crystal is demonstrated for the first time to our knowledge. Temperature and wavelength tuning of the crystal reveal the uniformity of the pattern while angle tuning reveals the dense nature of the crystal's Fourier spectrum. These results compare well with theoretical predictions showing the excellent uniformity of the crystal and suggest that more-complicated nonlinear holograms should be possible.
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| 23. |
- Brewer, Courtney A., et al.
(författare)
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Single-shot extreme ultraviolet laser imaging of nanostructures with wavelength resolution
- 2008
-
Ingår i: Optics Letters. - : Optical Society of America. - 0146-9592 .- 1539-4794. ; 33:5, s. 518-520
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Tidskriftsartikel (refereegranskat)abstract
- We have demonstrated near-wavelength resolution microscopy in the extreme ultraviolet. Images of 50 nm diameter nanotubes were obtained with a single ~1 ns duration pulse from a desktop-size 46.9 nm laser. We measured the modulation transfer function of the microscope for three different numerical aperture zone plate objectives, demonstrating that 54 nm half-period structures can be resolved. The combination of near-wavelength spatial resolution and high temporal resolution opens myriad opportunities in imaging, such as the ability to directly investigate dynamics of nanoscale structures.
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| 24. |
- Brunzell, Martin, et al.
(författare)
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Intra-cavity dark pulse generation through synchronized sum-frequency mixing
- 2022
-
Ingår i: Optics Letters. - : Optica Publishing Group. - 0146-9592 .- 1539-4794. ; 47:5, s. 1105-1108
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Tidskriftsartikel (refereegranskat)abstract
- A Nd:YVO4 laser operating at 1064 nm generating a stable mode-locked train of 10 ps-long dark pulses with a 211 MHz repetition rate is presented. The mode-locking relies on a periodic loss modulation produced by intra-cavity sum-frequency mixing with a synchronous bright-pulse train from a mode-locked femtosecond Yb:KYW laser at 1040 nm. A modulation depth of 9050 was achieved for the dark pulses, confirmed by cross-correlation measurements. The ultrafast loss modulation injects power into the Nd:YVO4 laser cavity modes beyond the laser gain bandwidth. At proper laser cavity length, the detuning interaction of these modes with the lasing modes leads to the generation of periodic ultra-fast transients at frequencies above 1.5 THz.
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| 25. |
- Burvall, Anna, et al.
(författare)
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Communication modes in large-aperture approximation
- 2007
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 32:6, s. 611-613
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Tidskriftsartikel (refereegranskat)abstract
- Simplified versions of the communication modes in the Fresnel domain are derived when the system apertures are large. The approximate modes, which are in the form of spherical waves and sinc functions with a spherical curvature, give physical insight into the communication modes approach and the basic limits of free-space optical communication systems. They also show that Gabor's information theory is readily derived from the communication modes.
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| 26. |
- Cai, Yangjian, et al.
(författare)
-
Average intensity and spreading of an elliptical Gaussian beam propagating in a turbulent atmosphere
- 2006
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 31:5, s. 568-570
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Tidskriftsartikel (refereegranskat)abstract
- An analytical formula for the average intensity of an elliptical Gaussian beam (EGB) propagating in a turbulent atmosphere is derived. The spreading properties of an EGB in a turbulent atmosphere are studied. It is found that an EGB will eventually become a circular Gaussian beam in a turbulent atmosphere. This interesting phenomenon is quite different from the propagation of an EGB in free space. The evolution properties are closely related to the parameters of the beam and the turbulent atmosphere
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| 27. |
- Cai, Yangjian, et al.
(författare)
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Lensless imaging with partially coherent light
- 2007
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 32:3, s. 205-207
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Tidskriftsartikel (refereegranskat)abstract
- Based on the fourth-order correlation of light, lensless imaging with incoherent or partially coherent light is investigated theoretically by use of classical optical coherence theory. A novel lensless optical system for implementing imaging is proposed. The visibility and quality of the image are influenced by the coherence and transverse size of the light source. The results suggest useful imaging applications in x-ray, gamma-ray, or other wavelengths where no effective lens is available, and they have potential applications in optical metrology and holography.
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| 28. |
- Cai, Yangjian, et al.
(författare)
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Lensless optical implementation of the coincidence fractional Fourier transform
- 2006
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 31:15, s. 2278-2280
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Tidskriftsartikel (refereegranskat)abstract
- A lensless optical system for implementing the coincidence fractional Fourier transform (FRT) is proposed. The conditions for the lensless optical system to implement the coincidence FRT with incoherent light and entangled photon pairs are discussed. The results offer a novel scheme for FRTs and thus suggest useful applications.
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| 29. |
- Cai, Yangjian, et al.
(författare)
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Propagation of partially coherent twisted anisotropic Gaussian Schell-model beams through an apertured astigmatic optical system
- 2006
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 31:6, s. 685-687
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Tidskriftsartikel (refereegranskat)abstract
- By expanding the hard-aperture function into a finite sum of complex Gaussian functions, we derived an approximate analytical formula for a partially coherent twisted anisotropic Gaussian Schell-model (AGSM) beam propagating through an apertured paraxial general astigmatic (GA) optical system by use of a tenser method. The results obtained by using the approximate analytical formula are in good agreement with those obtained by using the numerical integral calculation. Our formulas avoid time-consuming numerical integration and provide a convenient and effective way for studying the propagation and transformation of a partially coherent twisted AGSM beam through an apertured paraxial GA optical system. (c) 2006 Optical Society of America.
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| 30. |
- Camacho, Miguel, et al.
(författare)
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Designer surface plasmon dispersion on a one-dimensional periodic slot metasurface with glide symmetry
- 2017
-
Ingår i: Optics Letters. - : Optical Society of America. - 0146-9592 .- 1539-4794. ; 42:17, s. 3375-3378
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Tidskriftsartikel (refereegranskat)abstract
- In this Letter, we explore the dispersion of spoof surface plasmons supported by a single-layer glide-symmetric structure. This structure consists of an infinitely long double-notched slot perforated in a metal layer. The presence of a degeneracy of the two lowest-order modes at the Brillouin zone boundary, which have non-zero group velocity is explained and experimentally demonstrated. Further, the dependence of the band structure when glide-symmetric configuration is broken is also explored.
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| 31. |
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| 32. |
- Candiani, Alessandro, et al.
(författare)
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Optofluidic magnetometer developed in a microstructured optical fiber
- 2012
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 37:21, s. 67-69
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Tidskriftsartikel (refereegranskat)abstract
- A directional, in-fiber optofluidic magnetometer based on a microstructured optical fiber (MOF) Bragg-grating infiltrated with a ferrofluidic defect is presented. Upon application of a magnetic field, the ferrofluidic defect moves along the length of the MOF Bragg grating, modifying its reflection spectrum. The magnetometer is capable of measuring magnetic fields from 317 to 2500 G. The operational principle of such in-fiber magnetic field probe allows the elaboration of directional measurements of the magnetic field flux.
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| 33. |
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| 34. |
- Carpenter, J., et al.
(författare)
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Complete spatiotemporal characterization and optical transfer matrix inversion of a 420 mode fiber
- 2016
-
Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 41:23, s. 5580-5583
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Tidskriftsartikel (refereegranskat)abstract
- © 2016 Optical Society of America. The ability to measure a scattering medium's optical transfer matrix, the mapping between any spatial input and output, has enabled applications such as imaging to be performed through media which would otherwise be opaque due to scattering. However, the scattering of light occurs not just in space, but also in time. We complete the characterization of scatter by extending optical transfer matrix methods into the time domain, allowing any spatiotemporal input state at one end to be mapped directly to its corresponding spatiotemporal output state. We have measured the optical transfer function of a multimode fiber in its entirety; it consists of 420 modes in/out at 32768 wavelengths, the most detailed complete characterization of multimode waveguide light propagation to date, to the best of our knowledge. We then demonstrate the ability to generate any spatial/polarization state at the output of the fiber at any wavelength, as well as predict the temporal response of any spatial/polarization input state.
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| 35. |
- Che, Di, et al.
(författare)
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400-Gb/s direct modulation using a DFB plus R laser
- 2020
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Ingår i: Optics Letters. - : Optical Society of America. - 0146-9592 .- 1539-4794. ; 45:12, s. 3337-3339
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a direct-modulation and direct-detection system with a back-to-back line rate of 411.6 (net bit rate of 337.5) Gb/s using a 65 GHz DFB+R laser. The O-band laser with a chirp parameter of 0.6 supports dispersiontolerant transmissions up to 15 km without an optical amplifier.
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| 36. |
- Chen, D., et al.
(författare)
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Multiple fiber Bragg grating interrogation based on a spectrum-limited Fourier domain mode-locking fiber laser
- 2008
-
Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 33:13, s. 1395-1397
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Tidskriftsartikel (refereegranskat)abstract
- A novel fiber Bragg grating (FBG) sensing system based on a spectrum-limited Fourier domain mode-locking (SL-FDML) fiber laser is proposed. Multiple FBGs cascaded in a long fiber are utilized as both the sensors in the system and the wavelength-selected components in the SL-FDML fiber laser. Both wavelength-division multiplexing and spatial-division multiplexing techniques are demonstrated for interrogation of multiple FBGs by mapping the wavelength measurement to the time measurement and by adjusting the driving frequency of the SL-FDML fiber laser. The proposed FBG sensing system, employing techniques of the wavelength- and spatial-domain interrogation of multiple FBGs, can be used in remote and quasi-distributed multipoint sensing.
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| 37. |
- Chen, Xingxing, et al.
(författare)
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Near-infrared broadband absorber with film-coupled multilayer nanorods
- 2013
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Ingår i: Optics Letters. - : Optical Society of America. - 0146-9592 .- 1539-4794. ; 38:13, s. 2247-2249
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Tidskriftsartikel (refereegranskat)abstract
- Turning the surfaces of noble metals (metasurfaces) into black (highly absorptive) surfaces can be potentially applied in thermophotovoltaics, sensing, tailoring thermal emissivity, etc. Here we demonstrate an extremely broadband absorber for the 900-1600 nm wavelength range with robust high absorption efficiency. The inexpensive droplet evaporation method is implemented to create patterns of nanoparticles dispersed on a gold film spaced by a thin dielectric layer. The diversity of the complicated random stacking of the chemically synthesized gold nanorods is the major factor for the broad absorption band. Such a metamaterial absorber may pave the way for cost-effective manufacture of large-area black metasurfaces.
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| 38. |
- Chi, Kequn, et al.
(författare)
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Large-scale nanostructured low-temperature solar selective absorber
- 2017
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Ingår i: Optics Letters. - : Optical Society of America. - 0146-9592 .- 1539-4794. ; 42:10, s. 1891-1894
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Tidskriftsartikel (refereegranskat)abstract
- A large-scale nanostructured low-temperature solar selective absorber is demonstrated experimentally. It consists of a silicon dioxide thin film coating on a rough refractory tantalum substrate, fabricated based simply on self-assembled, closely packed polystyrene nanospheres. Because of the strong light harvesting of the surface nanopatterns and constructive interference within the top silicon dioxide coating, our absorber has a much higher solar absorption (0.84) than its planar counterpart (0.78). Though its absorption is lower than that of commercial black paint with ultra-broad absorption, the greatly suppressed absorption/emission in the long range still enables a superior heat accumulation. The working temperature is as high as 196.3 degrees C under 7-sun solar illumination in ambient conditions-much higher than those achieved by the two comparables.
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| 39. |
- Chi, Xiaoming, et al.
(författare)
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Fractal superconducting nanowire single-photon detectors with reduced polarization sensitivity
- 2018
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Ingår i: Optics Letters. - : OPTICAL SOC AMER. - 0146-9592 .- 1539-4794. ; 43:20, s. 5017-5020
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate superconducting nanowire single-photon detectors (SNSPDs) based on a fractal design of the nanowires to reduce the polarization sensitivity of detection efficiency. We patterned niobium titanium nitride thin films into Peano curves with a linewidth of 100 nm and integrated the nanowires with optical microcavities to enhance their optical absorption. At a base temperature of 2.6 K, the fractal SNSPD exhibited a polarization-maximum device efficiency of 67% and a polarization-minimum device efficiency of 61% at a wavelength of 1550 nm. Therefore, the polarization sensitivity, defined as their ratio, was 1.1, lower than the polarization sensitivity of the SNSPDs in the meander design. The reduced polarization sensitivity of the detector could be maintained for higher-order spatial modes in multimode optical fibers and could tolerate misalignment between the optical mode and the detector. This fractal design is applicable to both amorphous and polycrystalline materials that are commonly used for making SNSPDs.
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| 40. |
- Conforti, Matteo, et al.
(författare)
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Broadband parametric processes in chi((2)) nonlinear photonic crystals
- 2014
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 39:12, s. 3457-3460
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Tidskriftsartikel (refereegranskat)abstract
- We develop a general model, based on a (2 + 1)D unidirectional pulse propagation equation, for describing broadband noncollinear parametric interactions in 2D quadratic lattices. We apply it to the analysis of twin-beam optical parametric generation in hexagonally poled LiTaO3, gaining further insights into experimental observations.
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| 41. |
- Costa Dos Santos, Alan, 1991-, et al.
(författare)
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Multipartite entanglement encoded in the photon-number basis by sequential excitation of a three-level system
- 2023
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 48:23, s. 6332-6335
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Tidskriftsartikel (refereegranskat)abstract
- We propose a general scheme to generate entanglement encoded in the photon-number basis, via a sequential resonant two-photon excitation of a three-level system. We apply it to the specific case of a quantum dot three-level system, which can emit a photon pair through a biexciton–exciton cascade. The state generated in our scheme constitutes a tool for secure communication, as the multipartite correlations present in the produced state may provide an enhanced rate of secret communication with respect to a perfect GHZ state.
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| 42. |
- Cui, Y. X., et al.
(författare)
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Enhancing extraordinary transmission of light through a metallic nanoslit with a nanocavity antenna
- 2009
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 34:1, s. 16-18
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Tidskriftsartikel (refereegranskat)abstract
- The extraordinary transmission of light through a vertical nanoslit in a metal film is enhanced by introducing a nanocavity antenna formed by a nearby metallic nanostrip over the slit opening. For a fixed wavelength, the width of the metallic nanostrip should be chosen to make the horizontal metal-insulator-metal waveguide of finite length resonant as a Fabry-Perot cavity. When such a cavity antenna is used to enhance the transmission through a nonresonant nanoslit, the slit should be opened at a position with a maximal magnetic field in the horizontal resonant cavity. It is shown that an optimized cavity antenna can enhance greatly the transmission of light through a nonresonant nanoslit (by about 20 times) or a resonant nanoslit (by 124%). Such a transmission enhancement with a nanocavity antenna is studied for the first time, and the physical mechanism is explained.
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| 43. |
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| 44. |
- De Luca, Eleonora, et al.
(författare)
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Gallium Indium Phosphide Microstructures with Suppressed Photoluminescence for Applications in Nonlinear Optics
- 2019
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Ingår i: Optics Letters. - : Optical Society of America. - 0146-9592 .- 1539-4794. ; 44:21
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Tidskriftsartikel (refereegranskat)abstract
- Gallium indium phosphide (Ga0.51In0.49P), lattice matched to gallium arsenide, shows remarkable second-order nonlinear properties, as well as strong photoluminescence due to its direct band gap. By measuring the second-harmonic generation from the GaInP microwaveguide (0.2 x 11 x 1300 μm) before and after stimulating intrinsic photobleaching, we demonstrate that the photoluminescence could be strongly suppressed (-34 dB), leaving the nonlinear properties unchanged, making it suitable for low-noise applications.
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| 45. |
- de Oliveira, Vinicius Silva, et al.
(författare)
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Intensity noise optimization of a mid-infrared frequency comb difference-frequency generation source
- 2020
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 45:7, s. 1914-1917
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Tidskriftsartikel (refereegranskat)abstract
- We experimentally demonstrate in a difference-frequency generation mid-infrared frequency comb source the effect of temporal overlap between pump and signal pulses on the relative intensity noise (RIN) of the idler pulse. When scanning the temporal delay between our 130 fs long signal and pump pulses, we observe a RIN minimum with a 3 dB width of 20 fs delay and a RIN increase of 20 dB in 40 fs delay at the edges of this minimum. We also demonstrate active long-term stabilization of the mid-infrared frequency comb source to the temporal overlap setting corresponding to the lowest RIN operation point by an online RIN detector and active feedback control of the pump-signal pulse delay. This active stabilization setup allows us to dramatically increase the signal-to-noise ratio of mid-infrared absorption spectra. (C) 2020 Optical Society of America
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| 46. |
- Dev Choudhury, Bikash, et al.
(författare)
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Surface second harmonic generation from silicon pillar arrays with strong geometrical dependence
- 2015
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 40:9, s. 2072-2075
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Tidskriftsartikel (refereegranskat)abstract
- We present experimental demonstration and analysis of enhanced surface second harmonic generation (SHG) from hexagonal arrays of silicon pillars. Three sets of Si pillar samples with truncated cone-shaped pillar arrays having periods of 500, 1000, and 2000 nm, and corresponding average diameters of 200, 585 and 1550 nm, respectively, are fabricated by colloidal lithography and plasma dry etching. We have observed strong dependence of SHG intensity on the pillar geometry. Pillar arrays with a 1000 nm period and a 585 nm average diameter give more than a one order of magnitude higher SHG signal compared to the other two samples. We theoretically verified the dependence of SHG intensity on pillar geometry by finite difference time domain simulations in terms of the surface normal E-field component. The enhanced surface SHG light can be useful for nonlinear silicon photonics, surface/interface characterization, and optical biosensing.
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| 47. |
- Dombi, Peter, et al.
(författare)
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Conversion of chirp in fiber compression
- 2014
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Ingår i: Optics Letters. - : Optical Society of America. - 0146-9592 .- 1539-4794. ; 39:8, s. 2232-2235
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Tidskriftsartikel (refereegranskat)abstract
- Focusing positively chirped femtosecond pulses into nonlinear fibers provides significant spectral broadening and compression at higher pulse energies than achievable conventionally because self-focusing and damage are avoided. Here, we investigate the transfer of input to output chirp in such an arrangement. Our measurements show that the group delay dispersion of the output pulse, originating from the nonlinearities, is considerably reduced as compared to the initial value, by about a factor of 10. The mechanism of chirp reduction is understood by an interplay of self-phase modulation with initial chirp within the fiber. A simple model calculation based on this picture yields satisfactory agreement with the observations and predicts significant chirp reduction for input pulses up to the μJ regime. In practice, the reduction of chirp observed here allows for compressing the spectrally broadened intense pulses by ultrabroadband dispersive multilayer mirrors of quite moderate dispersion.
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| 48. |
- Dong, Hui, et al.
(författare)
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Quasi-monochromatic fiber depolarizer and its application to polarization-dependent loss measurement
- 2006
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 31:7, s. 876-878
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Tidskriftsartikel (refereegranskat)abstract
- We theoretically derive the relationship between the degrees of polarization (DOPs) of input and output for an optical component with polarization-dependent loss (PDL) and birefringence. Based on the theoretical result, we propose a novel depolarizer for quasi-monochromatic light that can depolarize a fully polarized light with a 50 MHz linewidth to less than 0.2% in the DOR The depolarized light is then used to measure PDL in a single-mode optical fiber link. To the best of our knowledge, our new PDL measurement method is significantly faster than all known methods. Experimental results show excellent agreement with other methods.
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| 49. |
- Dong, H., et al.
(författare)
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Quasi-monochromatic fiber depolarizer and its application to polarization-dependent loss measurement
- 2006
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Ingår i: Optics Letters. - : Optical Society of America. - 0146-9592 .- 1539-4794. ; 31:7, s. 876-878
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Tidskriftsartikel (refereegranskat)abstract
- We theoretically derive the relationship between the degrees of polarization (DOPs) of input and output for an optical component with polarization-dependent loss (PDL) and birefringence. Based on the theoretical result, we propose a novel depolarizer for quasi-monochromatic light that can depolarize a fully polarized light with a 50 MHz50 MHz linewidth to less than 0.2% in the DOP. The depolarized light is then used to measure PDL in a single-mode optical fiber link. To the best of our knowledge, our new PDL measurement method is significantly faster than all known methods. Experimental results show excellent agreement with other methods.
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| 50. |
- Dong, Lin, et al.
(författare)
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Photostability of lasing process from water solution of Rhodamine 6G with gold nanoparticles
- 2012
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 37:1, s. 34-36
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Tidskriftsartikel (refereegranskat)abstract
- We report the lasing performance and photobleaching of gain material containing a water solution of Rhodamine 6G dye and gold nanoparticles (NPs). In comparison to a pure dye solution, the investigated material demonstrated both enhancement and quenching of the lasing output, depending on the relative concentration of the gold NPs. Although the presence of NPs with an optimized concentration looks preferable in terms of the lasing output enhancement, such additives deteriorate the operational resource of the gain material; i.e., the photobleaching rate speeds up.
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