| 1. |
- Arafin, S., et al.
(författare)
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Comprehensive analysis of electrically-pumped GaSb-based VCSELs
- 2011
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Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 19:18, s. 17267-17282
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Tidskriftsartikel (refereegranskat)abstract
- This paper discusses several performance-related aspects of electrically-pumped GaSb-based buried tunnel junction VCSELs with an emission wavelength of 2.6 mu m based on theoretical and experimental results. These results allow a deeper insight into the internal device physics, such as radial diffusion of carriers, maximum continuous-wave operating temperature, diffraction loss, internal temperature, gain and loss parameters, internal quantum efficiency of the active region etc. These parameters can be taken into account while designing mid-infrared lasers which leads to an improved device performance. A simple thermal model of the devices based on the two-dimensional (2-D) finite element method using the material data from the literature is also presented. In addition, an application-based result utilizing these lasers for the measurement of absolute water vapor concentration by wavelength modulation spectroscopy (WMS) method are also described, hinting that devices are well-suited for the targeted sensing applications.
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| 2. |
- Baveja, P. P., et al.
(författare)
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Assessment of VCSEL thermal rollover mechanisms from measurements and empirical modeling
- 2011
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Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 19:16, s. 15490-15505
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Tidskriftsartikel (refereegranskat)abstract
- We use an empirical model together with experimental measurements for studying mechanisms contributing to thermal rollover in vertical-cavity surface-emitting lasers (VCSELs). The model is based on extraction of the temperature dependence of threshold current, internal quantum efficiency, internal optical loss, series resistance and thermal impedance from measurements of output power, voltage and lasing wavelength as a function of bias current over an ambient temperature range of 15-100 degrees C. We apply the model to an oxide-confined, 850-nm VCSEL, fabricated with a 9-mu m inner-aperture diameter and optimized for highspeed operation, and show for this specific device that power dissipation due to linear power dissipation (sum total of optical absorption, carrier thermalization, carrier leakage and spontaneous carrier recombination) exceeds power dissipation across the series resistance (quadratic power dissipation) at any ambient temperature and bias current. We further show that the dominant contributors to self-heating for this particular VCSEL are quadratic power dissipation, internal optical loss, and carrier leakage. A rapid reduction of the internal quantum efficiency at high bias currents (resulting in high temperatures) is identified as being the major cause of thermal rollover. Our method is applicable to any VCSEL and is useful for identifying the mechanisms limiting the thermal performance of the device and to formulate design strategies to ameliorate them.
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| 3. |
- Borgentun, Carl, 1979, et al.
(författare)
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Direct measurement of the spectral reflectance of OP-SDL gain elements under optical pumping
- 2011
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Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 19:18, s. 16890-16897
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Tidskriftsartikel (refereegranskat)abstract
- We report on a direct measurement method for acquiring highly precise reflectance spectra of gain elements for semiconductor disk lasers under optical pumping. The gain element acts as an active mirror, and the active mirror reflectance (AMR) was measured with a weak and tunable probe beam coincident on the gain element with a high-power pump beam. In particular, we measured the spectral AMR of a gain element designed to have a broad and flat AMR spectrum by being anti-resonant at the center wavelength and employing a parametrically optimized anti-reflection structure. We were able to confirm that this sophisticated gain element performs according to design, with an almost constant AMR of ~103% over a wavelength range of nearly 35 nm, very well matching the simulated behavior. Such gain characteristics are useful for optically pumped semiconductor disk lasers (OP-SDLs) designed for broadband tuning and short-pulse generation through mode-locking. The measurement technique was also applied to a conventional resonant periodic gain element designed for fixed wavelength OP-SDL operation; its AMR spectrum is markedly different with a narrow peak, again in good agreement with the simulations.
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| 4. |
- Girardi, Marcello, 1991, et al.
(författare)
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Multilayer integration in silicon nitride: decoupling linear and nonlinear functionalities for ultralow loss photonic integrated systems
- 2023
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Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 31:19, s. 31435-31446
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Tidskriftsartikel (refereegranskat)abstract
- Silicon nitride is an excellent material platform for its extremely low loss in a large wavelength range, which makes it ideal for the linear processing of optical signals on a chip. Moreover, the Kerr nonlinearity and the lack of two-photon absorption in the near infrared enable efficient nonlinear optics, e.g., frequency comb generation. However, linear and nonlinear operations require distinct engineering of the waveguide core geometry, resulting in a tradeoff between optical loss and single-mode behavior, which hinders the development of high-performance, ultralow-loss linear processing blocks on a single layer. Here, we demonstrate a dual-layer photonic integration approach with two silicon-nitride platforms exhibiting ultralow optical losses, i.e., a few dB/m, and individually optimized to perform either nonlinear or linear processing tasks. We demonstrate the functionality of this approach by integrating a power-efficient microcomb with an arrayed waveguide grating demultiplexer to filter a few frequency comb lines in the same monolithically integrated chip. This approach can significantly improve the integration of linear and nonlinear optical elements on a chip and opens the way to the development of fully integrated processing of Kerr nonlinear sources.
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| 5. |
- Haglund, Erik, 1985, et al.
(författare)
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Demonstration of post-growth wavelength setting of VCSELs using high-contrast gratings
- 2016
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Ingår i: Optics Express. - : The Optical Society. - 1094-4087 .- 1094-4087. ; 24:3, s. 1999-2005
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate, for the first time, post-growth wavelength setting of electrically-injected vertical-cavity surface-emitting lasers (VCSELs) by using high-contrast gratings (HCGs) with different grating parameters. By fabricating HCGs with different duty cycle and period, the HCG reflection phase can be varied, in effect giving different optical cavity lengths for HCG-VCSELs with different grating parameters. This enables fabrication of monolithic multi-wavelength HCG-VCSEL arrays for wavelength-division multiplexing (WDM). The GaAs HCG is suspended in air by removing a sacrificial layer of InGaP. Electrically-injected 980-nm HCG-VCSELs with sub-mA threshold currents indicate high reflectivity from the GaAs HCGs. Lasing over a wavelength span of 15 nm was achieved, enabling a 4-channel WDM array with 5 nm channel spacing. A large wavelength setting span was enabled by an air-coupled cavity design and the use of only the HCG as top mirror.
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| 6. |
- Haglund, Erik, 1985, et al.
(författare)
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High-power single transverse and polarization mode VCSEL for silicon photonics integration
- 2019
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Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 27:13, s. 18892-18899
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Tidskriftsartikel (refereegranskat)abstract
- © 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement. We demonstrate a 6.5 mW single transverse and polarization mode GaAs-based oxide-confined VCSEL at 850 nm. High power is enabled by a relatively large oxide aperture and an epitaxial design for low resistance, low optical loss, and high slope efficiency VCSELs. With the oxide aperture supporting multiple polarization unrestrained transverse modes, single transverse and polarization mode operation is achieved by a transverse and polarization mode filter etched into the surface of the VCSEL. While the VCSEL is specifically designed for light source integration on a silicon photonic integrated circuit, its performance in terms of power, spectral purity, polarization, and beam properties are of great interest for a large range of applications.
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| 7. |
- Haglund, Emanuel, 1988, et al.
(författare)
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Silicon-integrated short-wavelength hybrid-cavity VCSEL
- 2015
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Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 23:26, s. 33634-33640
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a short-wavelength hybrid-cavity vertical-cavity surface-emitting laser (VCSEL) heterogeneously integrated on silicon. A GaAs-based “half-VCSEL” has been attached to a dielectric distributed Bragg reflector (DBR) on a silicon wafer using ultra-thin divinylsiloxane-bis-benzocyclobutene (DVS-BCB) adhesive bonding, thereby creating a cavity with the standing-wave optical field extending over the silicon- and GaAs-based parts of the cavity. A 9 µm oxide aperture diameter VCSEL with a threshold current of 1.2 mA produces 1.6 mW optical output power at 6.0 mA bias current with a wavelength of ~845 nm.
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| 8. |
- Hu, Xiaonan, 1988, et al.
(författare)
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Si3N4 photonic integration platform at 1 µm for optical interconnects
- 2020
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Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 28:9, s. 13019-13031
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Tidskriftsartikel (refereegranskat)abstract
- Vertical-cavity surface-emitting lasers (VCSELs) are the predominant technology for high-speed short-range interconnects in data centers. Most short-range interconnects rely on GaAs-based multi-mode VCSELs and multi-mode fiber links operating at 850 nm. Recently, GaAs-based high-speed single-mode VCSELs at wavelengths > 1 µm have been demonstrated, which increases the interconnect reach using a single-mode fiber while maintaining low energy dissipation. If a suitable platform for passive wavelength- and space-multiplexing were developed in this wavelength range, this single-mode technology could deliver the multi-Tb/s interconnect capacity that will be required in future data centers. In this work, we show the first passive Si3N4 platform in the 1-µm band (1030-1075 nm) with an equivalent loss < 0.3 dB/cm, which is compatible with the system requirements of high-capacity interconnects. The waveguide structure is optimized to achieve simultaneously single-mode operation and low bending radius, and we demonstrate a wide range of high-performance building blocks, including arrayed waveguide gratings, Mach-Zehnder interferometers, splitters and low-loss fiber interfaces. This technology could be instrumental in scaling up the capacity and reducing the footprint of VCSEL-based optical interconnects and, thanks to the broad transparency in the near-infrared and compatibility with the Yb fiber amplifier window, enabling new applications in other domains as optical microscopy and nonlinear optics.
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| 9. |
- Szczerba, Krzysztof, 1985, et al.
(författare)
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30 Gbps 4-PAM transmission over 200m of MMF using an 850 nm VCSEL
- 2011
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Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 19:26, s. B203-B208
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Tidskriftsartikel (refereegranskat)abstract
- We present high speed real time, error free 4-PAMtransmissionfor short range optical links based on a VCSEL operating at 850 nm, a multimode fibre and a simple intensity detector. Transmission speeds of 25 Gbps and 30 Gbps are demonstrated, and the maximum fibre reaches were 300 m and 200 m, respectively. The 4-PAM is also compared with OOK transmission at 25 Gbps, and we find that at this bit rate 4-PAM increases the error free transmission distance in the multimode fibre by 100 m, compared to OOK.
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| 10. |
- Szczerba, Krzysztof, 1985, et al.
(författare)
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Experimental comparison of modulation formats in IM/DD links
- 2011
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Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 19:10, s. 9881-9889
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Tidskriftsartikel (refereegranskat)abstract
- We present an experimental comparison of modulation formatsfor optical intensity modulated links with direct detection. Specifically, wecompare OOK, QPSK on an electrical subcarrier and a new modulationformat named OOPSK. The OOPSK modulation format is shown to havebetter sensitivity than the other modulation formats, in agreement withtheoretical predictions. The impact of propagation in multimode fiber isalso studied and the results show that all modulation formats have similarsensitivity penalties, with respect to the fibre length.
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