An AlGaAs laser with high-quality dry etched mirrors fabricatedusing an ultrahigh vacuum in situ dry etching and deposition processingsystem

Highly reliable AlGaAs lasers with dry etched mirrors have been successfully fabricated with an ultrahigh-vacuum in situ processing system, equipped with reactive ion-beam etching (RIBE) and dielectric film deposition chambers. Etched mirror surfaces are protected against air-exposure contamination and nonvolatile-reaction-products adsorption with in situ Al₂O₃ passivation subsequent to the CI₂ RIBE mirror formation. Ion-bombardment-induced damage is repaired by thermal annealing. The annealing effect is enhanced by a contamination-free interface between the etched mirror surface and Al ₂O₃ passivation film. The lasers exhibit an increase in catastrophic optical damage (COD) level and long-life operation. Their COD levels are twice as high as that for as-etched lasers and are almost the same as those for conventional cleaved lasers     

Embedded-stripe GaAs-GaAlAs double-heterostructure lasers with polycrystalline GaAsP layers--II: Lasers with etched mirrors

Monolithic CW lasers with low threshold are reported in which mesa stripes are embedded with vapor-phase-grown high-resistivity GaAsP layers and cavity mirrors are formed by chemical etching. An etching solution consisting of NaOH, H2O2, and NH4OH has turned out to offer excellently flat-cavity mirrors on     

Room temperature operation of ultra-short quantum cascade lasers with deeply etched Bragg mirrors

Mid-infrared GaAs based bound-to-continuum quantum cascade microlasers with ridge waveguide geometry are fabricated by the monolithic integration of deeply etched semiconductor-air Bragg mirrors. Devices with ultra-short cavities of 50 and 150 /spl mu/m can be operated near room temperature (260 K) or at room temperature (300 K), respectively. 50 /spl mu/m-long devices show singlemode emission up to relatively high drive currents due to the large mode spacing of about 30 cm/sup -1/ (340 nm).     

高功率激光圆偏振镜的研究

本文研究了高功率激光圆偏振镜的理论分析计算和实验制备,获得了单片相移差为90°的多层介质膜结构的光学器件。     

50 mW CW-operated single-mode surface-emitting AlGaAs lasers with45° total reflection mirrors

The authors report on the fabrication and testing of surface-emitting AlGaAs 3.5 μm ridge lasers with etched mirrors and 45° internal deflectors. The 45° mirror coupling coefficient and the resulting threshold current penalty have been analyzed theoretically and experimentally. A surface-emitted optical power of 50 mW CW at 26 mA threshold current and external differential efficiency of 57% has been achieved in lateral fundamental-mode operation. The optical power density of 14 mW CW per micrometer ridge width is the highest reported to date and produces two-dimensional surface-emitting laser arrays of diffraction-limited beam quality suitable for optical storage applications     

Simple batch processing for forming high-reflective mirrors ofshort-cavity AlGaAs/GaAs lasers

A simple technology for fabricating a short-cavity AlGaAs/GaAs laser with a high-reflective mirror that is compatible with batch processing is described. Chlorine-assisted ion beam etching was used for providing one of the facet reflectors. For increased reflectivity, the etched facet was anodized and then metallized simultaneously with the p-contact metallization step. A threshold current of 8 mA for a six-quantum-well separate confinement structure was achieved with a cavity length of 50 μm     

Aging behavior and surge endurance of 870-900 nm AlGaAs lasers with nonabsorbing mirrors

The reliability of 870-900 nm AlGaAs TJS lasers has been investigated. An emission wavelength longer than 870 nm is realized by utilizing the band tailing effect due to heavy Zn-diffusion in the active region. A nonabsorbing mirror structure is employed to eliminate both gradual degradation and catastrophic damage of the facets. Stable continuous operation for over 10 000 hours has been confirmed at ambient temperatures higher than 50°C and output powers more than 5 mW/ facet. MTTF longer than 10⁵hours is expected for screened devices. Surge endurance has been improved to be nearly one order of magnitude higher than that for a conventional structure.     

Oscillation properties of AlGaAs DH lasers with an external grating

External control of the longitudinal oscillation mode of AlGaAs double heterostructure lasers using a diffraction grating is presented. Dependence of threshold current on selected mode wavelength is observed experimentally and is compared with a theory based on multilongitudinal mode rate equations. Baseband frequency responses for various bias currents above threshold are estimated by small-signal analysis and coincide well with experimental observations. Resonance frequency shifts to lower frequency and the resonance width is broadened by the optical feedback. Theoretical and experimental step pulse responses are also studied. Single longitudinal mode builds up rapidly. Relaxation oscillation observed after the oscillation builds up is less damped when mode selective feedback is provided. Output fluctuation frequency corresponds to the resonance frequency.     

Realization of GaAs/AlGaAs quantum-cascade lasers with high average optical power

Quasi-continuous-wave operation of GaAs/AlGaAs quantum-cascade lasers with high average optical power is demonstrated. Double X-ray diffraction has been used to investigate the quality of the epitaxial material. The compositional gradients and the interface quality are controlled effectively. The corrected average power of per facet about 17 mW and temperature tuning coefficient of the gain peak about 0.91 nm/K from 83 K to 140 K is achieved in pulse operation. Best value of threshold current density is less than 3.0 kA/cm² at 83 K.     

Low series resistance high-efficiency GaAs/AlGaAs vertical-cavity surface-emitting lasers with continuously graded mirrors grown by MOCVD

GaAs/AlGaAs vertical-cavity top-surface-emitting lasers (VCSELs) with a continuously graded mirror composition have been grown by MOCVD, and planar devices with proton-implant current confinement have been characterized. Continuous grading of the heterointerfaces in the Bragg reflectors eliminated the energy-band discontinuities, thus improving carrier transport and resulting in a substantial reduction in the series resistance and threshold voltage of the laser diodes. These VCSELs have excellent room-temperature CW electrical characteristics, including some of the lowest series resistances, highest power efficiencies and lowest operating voltages ever reported.<>     

High-reflectance dielectric mirrors deposited by plasma-enhanced chemical vapor deposition on GaAs-AlGaAs semiconductor lasers with inductively coupled plasma etched facets

High-reflectance dielectric mirrors (HRDMs) have been deposited on the etched facets of edge-emitting semiconductor ridge lasers. Dry etching using an inductively coupled plasma system formed the laser facets. The HRDMs were deposited using plasma enhanced chemical vapor deposition. Lasers with cavity lengths of 200 and 128 /spl mu/m have been tested before and after deposition of the HRDMs with a reduction in threshold of 50% and 61%, respectively. Lasing has been demonstrated in devices with cavity lengths as small as 32 /spl mu/m after the addition of the HRDMs.     

Record power characteristics of InGaAs/AlGaAs/GaAs heterostructure lasers

Continuous-wave output powers of 9.2 W at a constant heatsink temperature of 10°C and 12.2 W at a stabilized temperature of the active region have been obtained on an InGaAs/AlGaAs laser with a 0.4-μm-thick waveguide, operating at 1.03 μm. Record-breaking output mirror power densities of, respectively, 29.9 and 40 MW/cm² have been achieved without catastrophic optical mirror damage in the two temperature-stabilization regimes. A maximum power conversion efficiency of 66% has been achieved in a laser with a cavity length of 2 mm. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 35, No. 3, 2001, pp. 380–384. Original Russian Text Copyright ? 2001 by Livshits, Egorov, Kochnev, Kapitonov, Lantratov, Ledentsov, Nalyot, Tarasov. Deceased.     

Optical properties of reactive ion etched corner reflectorstrained-layer InGaAs-GaAs-AlGaAs quantum-well lasers

The optical properties of strained-layer InGaAs-GaAs-AlGaAs quantum-well lasers with a cavity comprised of a single cleaved facet and a dry etched corner reflector (CR) is described. For comparison, these data are contrasted with data for Fabry-Perot lasers made from the same material and having either two cleaved facets or one cleaved and one straight-etched facet. The etched CR exhibits higher overall reflectivity than the straight-etched and cleaved facet structures, resulting in lower threshold current density and higher efficiency. However, near-field measurements indicate that improvement in reflectivity from the etched CRs is offset by their tendency to favor off-order transverse modes     

Tunable GaInNAs lasers with photonic crystal mirrors

We present results of tunable GaInNAs lasers with photonic crystal (PhQ mirrors, fabricated from GaAs-AlGaAs layers with a double GaInNAs quantum well emitting at IR wavelength. The devices are realized as ridge waveguide lasers with two coupled segments and a total length between 240 and 580 pm. PhC blocks with different thicknesses are used for the back and front mirror as well as for the intermediate reflector between the two segments. The lasers have threshold currents around 20 mA and output powers up to 6 mW. Tuning of the laser emission over 30 nm is achieved by a variation of the currents injected into the two segments.     

Modal analysis of semiconductor lasers with nonplanar mirrors

We present a formalism for analyzing laser resonators which possess nonplanar mirrors and lateral waveguiding [e.g., an unstable resonator semiconductor laser (URSL)]. The electric field is expanded in lateral modes of the complex-index waveguide and is required to reproduce itself after, one roundtrip of the cavity. We show how the waveguide modes, their gain and loss, and hence the criterion for truncation of the infinite set of modes can be derived from the Green's function of the one-dimensional eigenvalue equation for the waveguide. Examples are presented for three cases of interest-a purely gain-guided URSL, an index-guided URSL, and a gain-guided tilted-mirror resonator. We compare theoretical calculations to previous experiments.     

High power and low optical feedback noise AlGaAs single quantum well lasers

GaAs-AlGaAs single quantum well self-aligned lasers have been developed for optical disc recording. The lasers emitting at 834 nm have realised low optical feedback noise as well as high output power. The lasers have shown less than -130 dB/Hz relative intensity noise at 3 mW, and stable 50 mW operation (over 500 hours at 50 degrees C ambient).<>     

GaInAsP/InP DH lasers with a chemically etched facet

We describe a new configuration and novel fabrication method for GaInAsP/InP DH lasers in which one of the facet mirrors is chemically etched and the other one is formed by cleaving. The etched facet is fabricated monolithically by wet chemical etching in a solution of HCl:CH3COOH:H2O2= (1:2:1). Broad-area contact lasers of this type operating at room temperature at a wavelength ofsim 1.3 mum have been demonstrated.     

Improved electrical and thermal properties of InP-AlGaAsSb Bragg mirrors for long-wavelength vertical-cavity lasers

The electrical, thermal and optical properties of n-doped InP-AlGaAsSb 1.5-/spl mu/m Bragg mirrors are reported. A voltage of 10 mV per pair at 1 kA/cm/sup 2/ has been obtained in these mirrors, due to a low conduction band offset. This record electrical performance, combined with a large refractive index contrast (n/sub H//n/sub L/=1.135) and improved thermal properties, makes the combination very promising for long wavelength vertical cavity surface emitting lasers.     

Frequency offset locking of AlGaAs semiconductor lasers

Frequency offset locking was proposed as a reliable electrical negative feedback technique for tracking and sweeping of a semiconductor laser frequency. A frequency stabilized laser was used as a master laser, whose residual frequency fluctuations were 140 (kHz) at the integration time (τ) of 100 msleq tau leq 100s. A digital phase comparator of a large dynamic range of2pi times 2^{11}(rad) was employed in the feedback loop to reduce the phase fluctuations of the beat signal between the master and slave lasers. Performances of frequency tracking and sweeping of the slave laser were quantitatively evaluated, and the results are: residual frequency fluctuations of the beat signal were reduced as low as 11 (Hz) attau = 100s, which meant that the residual frequency fluctuations of the slave laser were almost equal to those of the master laser, i.e., the slave laser frequency tracked accurately to the master laser frequency. Both the capture range and lock range of the beat frequency were 1.22 GHz. Frequency tunable range of the slave laser was 36.6 GHz under the condition of frequency offset locking, in which the slave laser frequency fluctuations were maintained as low as the one given above.     

Phased array of AlGaAs multistripe index-guided lasers

The fabrication and characteristics of a novel index-guided phase-locked array are described. A single-lobe far-field pattern was obtained up to the CW output of 100 mW in the 3-element diode laser.