| 441. |
- Liu, Hairong, et al.
(författare)
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Design and analysis of anti-resonant reflecting photonic crystal VCSEL lasers
- 2004
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Ingår i: Optics Express. - : Optical Society of America. - 1094-4087. ; 12:18, s. 4269-4274
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Tidskriftsartikel (refereegranskat)abstract
- Anti-resonant reflecting photonic crystal structure is employed in vertical cavity surface emitting lasers (VCSELs) to achieve photon confinement in lateral direction. Such a design is promising in supporting large-aperture single-mode emission. In the configuration, hexagonal arrays of high-index cylinders which run vertically in the cladding region are introduced in the VCSEL’s top DBR (p-DBR) mirror region. The transverse modal property of the proposed structure, especially leakage loss, has been theoretically investigated. An optimum design for the minimum radiation loss while maintaining single-mode operation has been discussed in this paper.
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| 442. |
- Liu, Haichun, et al.
(författare)
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Potential of multi-photon upconversion emissions for fluorescence diffuse optical imaging
- 2014
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Ingår i: Optics Express. - 1094-4087. ; 22:15, s. 17782-17790
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Tidskriftsartikel (refereegranskat)abstract
- The spatial resolution of fluorescence molecular imaging is a critical issue for the success of the technique in biomedical applications. One important method for increasing the imaging resolution is to utilize multi-photon emissions. In this study, we thoroughly investigate the potential of the multi-photon upconversion emissions from rare-earth-doped upconverting nanoparticles for the improvement in spatial resolution of diffuse optical imaging. It is found that the imaging resolution is increased by a factor of 1.45 through employing two-photon upconversion emission compared with using the linear emission, and can be further elevated by a factor of 1.23 by using three-photon upconversion emission. In addition, we demonstrate that the pulsed excitation approach holds the promise of overcoming the low quantum yield associated with the high-order upconversion emissions. (C) 2014 Optical Society of America
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| 443. |
- Liu, Hairong, et al.
(författare)
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Theoretical investigation on guiding IR light in hollow-core metallic fiber with corrugated inner surface
- 2010
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Ingår i: Optics Express. - 1094-4087. ; 18:21, s. 21959-21964
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Tidskriftsartikel (refereegranskat)abstract
- Hollow metallic fibers (HMFs) are in general lossy primarily owing to the fact that the guided transverse-magnetic (TM) light sustains a relatively high propagation loss. In this paper, we propose a type of practical hollow-core metallic fiber (HMF) with longitudinally corrugated inner surface for transmitting infrared (IR) light. Simulation results show that the loss of the fundamental TM mode can be easily reduced by 50 similar to 100 times compared to a HMF without surface corrugation. In contrast to the traditional HMF with a dielectric coating, it is shown that the loss of the fundamental TM mode in the proposed HMF is relatively insensitive to the corrugation layer thickness or equivalently the operating frequency.
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| 444. |
- Liu, Hairong, et al.
(författare)
-
Theoretical investigation on guiding IR light in hollow-core metallic fiber with corrugated inner surface
- 2010
-
Ingår i: Optics Express. - : Optical Society of America. - 1094-4087. ; 18:21, s. 21959-21964
-
Tidskriftsartikel (refereegranskat)abstract
- Hollow metallic fibers (HMFs) are in general lossy primarily owing to the fact that the guided transverse-magnetic (TM) light sustains a relatively high propagation loss. In this paper, we propose a type of practical hollow-core metallic fiber (HMF) with longitudinally corrugated inner surface for transmitting infrared (IR) light. Simulation results show that the loss of the fundamental TM mode can be easily reduced by 50~100 times compared to a HMF without surface corrugation. In contrast to the traditional HMF with a dielectric coating, it is shown that the loss of the fundamental TM mode in the proposed HMF is relatively insensitive to the corrugation layer thickness or equivalently the operating frequency.
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| 445. |
- Liu, Jianxin, et al.
(författare)
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A novel methodology to directly pre-determine the relative wavelength response of DFB laser in wavelength modulation spectroscopy
- 2019
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Ingår i: Optics Express. - : Optical Society of America. - 1094-4087. ; 27:2, s. 1249-1261
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Tidskriftsartikel (refereegranskat)abstract
- A novel methodology to directly pre-determine the relative wavelength response (RWR) of a DFB laser, in terms of a combined current linearly scanned wavelength response and current modulated wavelength response (CMWR), in wavelength modulation spectroscopy (WMS) is presented. It is shown that the assessed RWR can be used to mimic the measured response with standard deviation of discriminations that are below 3.4 x 10(-3)cm(-1) under a variety of conditions. It is also shown that its performance supersedes two commonly used assessment models of the CMWR but is slightly worse than that of the third model. however with the benefit of solely using a single fitting parameter (the concentration) instead of more. When the novel method is applied to the assessment of CO2 concentration in a Herriot-type multipass cell by using the technique of calibration-free WMS, the results show that there is virtually no difference compared to that by use of the best of the other methods. It is concluded that the novel method is more robust and simplifies the retrieval process of gas concentration.
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| 446. |
- Liu, Jianxin, et al.
(författare)
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Development of a Doppler-broadened NICE-OHMS system for trace gas detection based on a single sideband phase modulator
- 2021
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Ingår i: Optics Express. - : The Optical Society. - 1094-4087. ; 29:26, s. 42411-42419
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Tidskriftsartikel (refereegranskat)abstract
- To expand the applicability of noise-immune cavity-enhanced optical heterodyne molecular spectrometer (NICE-OHMS), a universal system incorporating a fiber-coupled singlesideband modulator (f-SSM) for control of the laser frequency has been developed. A homemade PID servo mainly composed of two integrators has been designed, resulting in a locking bandwidth of 170 kHz and a continuous tuning range of 2.2 GHz. The system exhibits a noise-equivalent Doppler-broadened absorption limit of 8.0x10-14 cm-1 for an integration time of 64 s. Since the f-SSM is the sole external frequency actuator, this opens up for NICE-OHMS based on a multitude of laser systems.
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| 447. |
- Liu, Jie, et al.
(författare)
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OCDMA PON supporting ONU inter-networking based on gain-switched Fabry-Perot lasers with external dual-wavelength injection
- 2010
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Ingår i: Optics Express. - 1094-4087. ; 18:22, s. 22982-22987
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Tidskriftsartikel (refereegranskat)abstract
- We propose and demonstrate an OCDMA-PON scheme with optical network unit (ONU) internetworking capability, which utilizes low-cost gain-switched Fabry-Perot (GS-FP) lasers with external dual-wavelength injection as the pulse sources on the ONU side. The injection-generated optical pulses in two wavelengths from the same GS-FP laser are used separately for the PON uplink transmission and ONU internetworking. Experimental results based on a two-user OCDMA system confirm the feasibility of the proposed scheme. With OCDMA technologies, separate ONU-internetworking groups can be established using different optical codes. We also give experiment results to analyze the performance of the ONU-ONU transmission at different power of interference signals when two ONU-internetworking groups are present in the OCDMA-PON.
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| 448. |
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| 449. |
- Liu, LIu, et al.
(författare)
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Near-field optical storage system using a solid immersion lens with a left-handed material slab
- 2004
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Ingår i: Optical express. - 1094-4087. ; 12, s. 4835-4840
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Tidskriftsartikel (refereegranskat)abstract
- A new near-field optical storage system utilizing a left-handed material (LHM) is introduced by attaching an LHM slab to the lower surface of a conventional solid immersion lens (SIL). The performance of the present storage system is compared with a conventional SIL system through numerical simulation. The LHM slab in the present storage system can image very well the focused spot at the lower surface of the SIL to the surface of a disc. It allows a large air-gap for the mechanical convenience while keeping a large signal contrast and a high storage density. The tolerance of the air-gap is also improved.
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| 450. |
- Liu, Liu, et al.
(författare)
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Novel surface plasmon waveguide for high integration
- 2005
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Ingår i: Optics Express. - 1094-4087. ; 13, s. 6645-6650
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Tidskriftsartikel (refereegranskat)abstract
- A novel surface plasmon waveguide structure is proposed for highly integrated planar lightwave circuits. By etching a small trench through a metallic thin film on a silica substrate, a guided mode with highly confined light fields is realized. The mode properties of the proposed structure are studied. The necessity of using a polymer upper-cladding is discussed. The coupling between two closely positioned waveguides and a 90° bending are also studied numerically. Sharp bending and high integration can be realized with the present surface plasmon waveguide. The proposed structure is easy to fabricate as compared with some other types of surface plasmon waveguides for high integration
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