InGaAsP (λ=1.3 μm) strip buried heterostructure lasersgrown by MOCVD

The authors describe InGaAsP-InP index guides strip buried heterostructure lasers (SBH) operating at 1.3 μm with a 1.1-μm guiding layer grown by a two-step atmospheric pressure metalorganic chemical vapor deposition (MOCVD) growth procedure. These lasers are compared with buried heterostructure lasers having similar guiding layers under the active layer but terminated at the edge of the active layer. SBH lasers with 0.15-μm-thick active layer strips, 5-μm wide, and guide layers varying from 0 to 0.7 μm have threshold currents increasing from 34 to 59 mA, and nearly constant differential external quantum efficiencies of 0.2 mW/mA. The threshold current increases more rapidly with temperature with increasing guide layer thickness, with T₀ decreasing from 70°C for lasers without a guide layer to 54.3°C for lasers without a guide layer to 54.3°C for lasers with 0.7-μm-thick guide layers. Output powers of up to 30 mW/facet have been obtained from 254-μm-long lasers and were found to be insensitive to guide layer thickness     

Barrier composition dependence of differential gain and externaldifferential quantum efficiency in 1.3-μm strained-layermultiquantum-well lasers

Dependence of the differential gain and the external differential quantum efficiency on the composition of InGaAsP barrier layers were investigated for 1.3 μm InGaAsP-InGaAsP compressively strained layer (SL) multiquantum well (MQW) lasers. In this investigation, we compared between SL-MQW lasers and unstrained MQW lasers having the same well thicknesses and the same emitting wavelength in order to clarify the effect of strain for each barrier composition. As a result It has been found that the barrier composition has large influence on the differential gain and the external differential quantum efficiency in the SL-MQW lasers. Narrower band-gap barrier means little effect of strain on the differential gain due to the electron overflow from a well layer, while wider band-gap barrier means degradation in the differential gain and the external differential quantum efficiency due to the nonuniform injection of hole into a well layer. In this experiment, the barrier composition of 1.05 μm is suitable for 1.3 μm InGaAsP-InGaAsP SL-MQW lasers to realize large differential gain and high external differential quantum efficiency simultaneously     

Low-threshold current, high-efficiency 1.3-μm wavelengthaluminum-free InGaAsN-based quantum-well lasers

We demonstrate high-performance Al-free InGaAsN-GaAs-InGaP-based long-wavelength quantum-well (QW) lasers grown on GaAs substrates by gas-source molecular beam epitaxy using a RF plasma nitrogen source. Continuous wave (CW) operation of InGaAsN-GaAs QW lasers is demonstrated at λ=1.3 μm at a threshold current density of only J_TH =1.32 kA/cm². These narrow ridge (W=8.5 μm) lasers also exhibit an internal loss of only 3.1 cm^-1 and an internal efficiency of 60%. Also, a characteristic temperature of T₀=150 K from 10°C to 60°C was measured, representing a significant improvement over conventional λ=1.3 μm InGaAsP-InP lasers. Under pulsed operation, a record high maximum operating temperature of 125°C and output powers greater than 300 mW (pulsed) and 120 mW (CW) were also achieved     

High T0 long-wavelength InGaAsN quantum-well lasersgrown by GSMBE using a solid arsenic source

We demonstrate high performance, λ=1.3- and 1.4-μm wavelength InGaAsN-GaAs-InGaP quantum-well (QW) lasers grown lattice-matched to GaAs substrates by gas source molecular beam epitaxy (GSMBE) using a solid As source. Threshold current densities of 1.15 and 1.85 kA/cm² at λ=1.3 and 1.4 μm, respectively, were obtained for the lasers with a 7-μm ridge width and a 3-mm-long cavity. Internal quantum efficiencies of 82% and 52% were obtained for λ=1.3 and 1.4 μm emission, respectively, indicating that nonradiative processes are significantly reduced in the quantum well at λ=1.3 μm due to reduced N-H complex formation. These Fabry-Perot lasers also show high characteristic temperatures of T₀ =122 K and 100 K at λ=1.3 and 1.4 μm, respectively, as well as a low emission wavelength temperature dependence of (0.39±0.01) nm/°C over a temperature range of from 10°C to 60°C     

Distributed-feedback quantum cascade lasers emitting in the 9-μmband with InP top cladding layers

Two different high performance quantum cascade distributed-feedback lasers with four quantum-well-based active regions and InP top cladding layers are presented. The first device, which emitted at 9.5 μm, was mounted junction down in order to get high average powers of up to 71 mW at -30°C and 30 mW at room temperature. The other device, which lased at 9.1 μm, was optimized for high pulsed operating temperatures and tested up to 150°C at 1.5% duty cycle. The emission of both lasers stayed single mode with more than 20-dB side-mode suppression ratio over the entire investigated power and temperature range     

High-performance strain-compensated InGaAs-GaAsP-GaAs(λ=1.17 μm) quantum well diode lasers

This letter reports studies on highly strained and strain-compensated InGaAs quantum-well (QW) active diode lasers on GaAs substrates, fabricated by low-temperature (550°C) metal-organic chemical vapor deposition (MOCVD) growth. Strain compensation of the (compressively strained) InGaAs QW is investigated by using either InGaP (tensile-strained) cladding layer or GaAsP (tensile-strained) barrier layers. High-performance λ=1.165 μm laser emission is achieved from InGaAs-GaAsP strain-compensated QW laser structures, with threshold current densities of 65 A/cm² for 1500-μm-cavity devices and transparency current densities of 50 A/cm². The use of GaAsP-barrier layers are also shown to significantly improve the internal quantum efficiency of the highly strained InGaAs-active laser structure. As a result, external differential quantum efficiencies of 56% are achieved for 500-μm-cavity length diode lasers     

Long-wavelength strained quantum-well lasers oscillating up to210°C on InGaAs ternary substrates

Long-wavelength InGaAs-InAlGaAs strained quantum-well lasers have been fabricated on In_0.22Ga_0.78As ternary substrates grown by the Bridgman method. The threshold current density and lasing wavelength at 20°C are 245 A/cm² and 1.226 μm, respectively. The device has lased up to 210°C, which is the highest operating temperature ever reported for long-wavelength semiconductor lasers. The temperature sensitivity of the slope efficiency between 20°C and 120°C is only -0.0051 dB/K, showing suppressed carrier overflow owing to deep potential quantum wells. These high-temperature durabilities of this laser are fascinating features for application to optical subscriber and optical interconnection systems     

Low dispersion penalty and wide temperature range operation over120 K with 1.55 μm strained MQW-DFB laser module

STM 16 (2.488 Gbit/s) system operation over a wide DFB chip temperature range of more than 120 K (from -25°C to +95°C) is presented with dispersion penalty below 1 dB after transmission across 100 km standard fibre. DFB operation at 1.55 μm with a high sidemode suppression ratio of 40 dB is achieved within -40°C to +95°C. The lasers were realised using a BRS lateral structure and a quaternary InGaAsP MQW stack with six compressively strained quantum wells and a highly detuned DFB grating     

Effect of thermionic electron emission from the active layer on theinternal quantum efficiency of InGaAsP lasers operating at 1.3μm

We have experimentally characterized the quantum efficiency in InGaAsP lasers operating at 1.3 μm. The observed reduction in external quantum efficiency with increasing temperature and increasing bias current is found to be caused almost entirely by a reduction of the internal quantum efficiency. The internal quantum efficiency is reduced approximately linearly with bias current in the temperature range investigated. The experimental results are well explained with a theoretical model based on thermionic emission of carriers out of the active region     

Strained 1.3 μm MQW AlGaInAs lasers grown by digital alloy MBE

AlGaInAs strained MQW lasers, emitting at 1.3 μm, have been prepared for the first time using a digital alloy approach. 2 μm stripe geometry lasers have characteristics comparable to those of lasers prepared using bulk alloy layers. The infinite length threshold current densities are as low as 140 kA/cm²/quantum well and T ₀ values (20-40°C) range from 75-90 K for chip lengths of 375-2375 μm     

High temperature, high power InGaAs/GaAs quantum-well lasers withlattice-matched InGaP cladding layers

The authors report the high-temperature and high-power operation of strained-layer InGaAs/GaAs quantum well lasers with lattice-matched InGaP cladding layers grown by gas-source molecular beam epitaxy. Self-aligned ridge waveguide lasers of 3-μm width were fabricated. These lasers have low threshold currents (7 mA for 250-μm-long cavity and 12 mA for 500-μm-long cavity), high external quantum efficiencies (0.9 mW/mA), and high peak powers (160 mW for 3-μm-wide lasers and 285 mW for 5-μm-wide laser) at room temperature under continuous wave (CW) conditions. The CW operating temperature of 185°C is the highest ever reported for InGaAs/GaAs/InGaP quantum well lasers, and is comparable to the best result (200°C) reported for InGaAs/GaAs/AlGaAs lasers     

Folded-cavity surface-emitting InGaAs-GaAs lasers withlow-threshold current density and high efficiency

Folded-cavity surface-emitting InGaAs-GaAs lasers (FCSELs) that employ high-quality internal 45° deflectors are demonstrated with low-threshold current density and high efficiency. A simplified process involving a stop etch to position the surface emitting output mirror close to the waveguide and ion-beam-etching (IBE) to form the 45° deflecting mirror is presented. FCSELs (cavity length 800 μm) with two 45° deflectors, are obtained with threshold current density as low as 112.5 A/cm² and surface-emission external quantum efficiency as high as 65% (0.82 W/A). The additional loss contributed by the folded-cavity design is estimated as 4.2 cm^-1     

High performance and high reliability of 1.55-μmcurrent-blocking grating complex-coupled DFB lasers

We report the high performance and high reliability of the 1.55 μm current-blocking grating complex-coupled InGaAsP strained distributed-feedback MQW lasers. Small variation in slope efficiency, high characteristic temperature, and high side mode suppression ratio have been achieved over a wide temperature range of 20°C-90°C. From the accelerated aging test, the median life at 25°C and 5 mW is estimated to be longer than 50 years     

Temperature-dependent characteristics of 1.3-μm AlGaInAs-InPlasers with multiquantum barriers at the guiding layers

Strain-compensated 1.3-μm AlGaInAs-InP multiquantum-well (MQW) lasers with multiquantum barriers at both the n- and p-type guiding layers are comprehensively studied. The laser exhibits a characteristic temperature as high as 95 K and degradation in slope efficiency as low as -1.06 dB in the temperature range from 25°C to 75°C. The characteristic temperature of transparency current density is deduced to be 129 K. It is also found that the internal loss increases slowly with temperature, while the temperature dependence of the internal quantum efficiency dominates the degradation of the external quantum efficiency due to the degradation of the stimulated recombination, and significant increase of electron and hole leakage at high temperature     

Extremely high power 1.48 μm GaInAsP/InP GRIN-SCH strained MQWlasers

A record CW output power of 360 mW at 25°C was achieved by investigating the structure of optical confinement layer in 1.48 μm GRIN-SCH MQW lasers. It is experimentally demonstrated that the use of a wide bandgap and thin SCH layer gives a high differential quantum efficiency without expense of threshold current. Low driving currents, 195 mA for 100 mW, 450 mA for 200 mW and 890 mA for 300 mW, were obtained in the optimized cavity lengths     

High temperature 10 Gbit/s directly modulated 1.3 μm DFB lasersusing InAsP/InGaAsP materials

Uncooled 10 Gbit/s direct modulation of high-power 1.3 μm InAsP/InGaAsP directly modulated multiple quantum well distributed feedback (DFB) lasers is demonstrated. High resonant frequencies and high efficiency at 85°C are obtained due to the high epitaxial quality of ternary, aluminium-free, quantum wells. Floor-free transmission on 90 and 140 ps/nm within ITU recommendations are demonstrated     

AlInGaAs/AlGaAs strained quantum-well ridge waveguide lasers grownby metalorganic chemical vapor deposition

AlInGaAs/AlGaAs strained quantum-well ridge waveguide diode lasers with an emission wavelength of 890 nm are presented. These devices exhibit both single spatial and longitudinal mode operation up to 30 mW of optical output power. A CW threshold current of 13 mA was obtained for a 5-μm-wide ridge waveguide having a cavity length of 500 μm. The differential quantum efficiency was 52%. The lateral and perpendicular far-field radiation patterns (FWHM) from the laser were 6° and 51°, respectively. Reliability testing on uncoated gain-guided lasers made from the same wafer showed no sudden death failures and degradation rates as low as 4.6%/kh     

Tapered waveguide InGaAs/InGaAsP multiple-quantum-well lasers

The use of ultrathin etch-stop techniques to expand the vertical optical mode size adiabatically in 1.5-μm InGaAs/InGaAsP MQW lasers using a tapered-core passive intracavity waveguide structure is discussed. 30% differential quantum efficiency out the tapered facet, far-field FWHM of ~12° and a butt-coupling efficiency into a cleaved fiber of -4.2 dB, with -1-dB alignment tolerances of ~±3 μm, were achieved     

Carrier loss in InGaAsP-InP lasers grown by hydride CVD

We have experimentally characterized the quantum efficiency in InGaAsP hydride CVD grown lasers operating at 1.3 μm. The observed reduction in external quantum efficiency with increasing temperature is found to be caused mostly by a reduction of the internal quantum efficiency. The experimental results are well explained with a theoretical model based on thermionic emission of carriers out of the active region. The model also helps to understand the difference in temperature performance between lasers studied in this paper and those grown by MOCVD     

Long-wavelength GaInNAs(Sb) lasers on GaAs

The boom in fiber-optic communications has caused a high demand for GaAs-based lasers in the 1.3-1.6-μm range. This has led to the introduction of small amounts of nitrogen into InGaAs to reduce the bandgap sufficiently, resulting in a new material that is lattice matched to GaAs. More recently, the addition of Sb has allowed further reduction of the bandgap, leading to the first demonstration of 1.5-μm GaAs-based lasers by the authors. Additional work has focused on the use of GaAs, GaNAs, and now GaNAsSb barriers as cladding for GaInNAsSb quantum wells. We present the results of photoluminescence, as well as in-plane lasers studies, made with these combinations of materials. With GaNAs or GaNAsSb barriers, the blue shift due to post-growth annealing is suppressed, and longer wavelength laser emission is achieved. Long wavelength luminescence out to 1.6 μm from GaInNAsSb quantum wells, with GaNAsSb barriers, was observed. In-plane lasers from these samples yielded lasers operating out to 1.49 μm, a minimum threshold current density of 500 A/cm² per quantum well, a maximum differential quantum efficiency of 75%, and pulsed power up to 350 mW at room temperature