Continuous-wave Threshold Current Research Articles

High performance InGaAs/GaAlAs laser diodes for electronic/photonic integrated circuit applications

High-performance, short-cavity, strained-layer InGaAs/GaAlAs laser diodes that are suitable for two-dimensional electronic-photonic integrated circuit (EPIC) applications have been demonstrated. Continuous-wave threshold currents as low as 4 mA, and singlemode output powers in excess of 100 mW (maximum output power: 120 mW) were achieved for as-cleaved, reactive-ion-etched, 3.5 μm-wide, 200 μm-long, InGaAs/GaAlAs ridge-waveguide laser diodes in the junction-side up configuration.

Continuous wave visible InGaP/InGaAlP quantum-well surface-emitting laser diodes

Vertical-cavity surface-emitting lasers in the 0.66 mu m visible spectral region were fabricated by metal-organic chemical vapor deposition. The laser structure consists of four In/sub 0.5/Ga/sub 0.5/P (80 AA)/In/sub 0.5/Al/sub 0.5/GaP (60AA) quantum wells as the active medium. The quantum wells are located in the middle of a one lambda -thick cavity spacer, which is sandwiched between two highly reflective staircase-distributed Bragg reflectors. The continuous wave threshold currents, I/sub th/, are 3.9 and 4.6 mA at -75 and -25 degrees C, respectively, for 15 mu m diameter devices. The lasers can also be operated at room temperature, but only in a pulsed mode with an I/sub th/ of 12 mA at 25 degrees C.

CBE growth of low threshold 1.5 μm InGaAs/InGaAsP MQW lasers

This paper reports on low-threshold InGaAs/InGaAsP multiple quantum well (MQW) lasers emitting at a wavelength of 1.52 μm. Separate confinement heterostructure (SCH) lasers were grown using chemical beam epitaxy (CBE) with source material pressure-control systems. A continuous wave threshold current of 12 mA and internal quantum efficiency of 73% (both facets) are observed in uncoated double-channel planar buried heterostructure (DCPBH) lasers. The internal loss is 15 cm -1. More than 90% of 50 laser chips have a threshold current of 15±3 mA.

Long-wavelength InGaAsP/InP distributed feedback lasers incorporating gain-coupled mechanism

Successful operation of long-wavelength InGaAsP low-threshold-current gain-coupled DFB lasers was demonstrated by using an InGaAsP quaternary grating that absorbs the DFB (distributed feedback) emission. The amount of gain (loss)-coupling is controlled by the composition (bandgap) and thickness of the grating quaternary and the InP-spacer layer between the grating and the active layer. With optimally designed lasers, CW (continuous-wave) threshold currents were 10-15 mA (250- mu m cavity, as-cleaved), slope efficiency was approximately 0.4 mW/mA (both facets) and SMSR (side-mode suppression ratio) was as high as 52 dB. The laser operated in the same DFB mode with SMSR staying approximately 50 dB throughout the entire current range. At 100 degrees C, the CW threshold current stayed low, approximately 50 mA, and SMSR was approximately 40 dB. Results also indicate that the presence of gain-coupling removes the degeneracy in lasing wavelength. >

Design and fabrication of ridge waveguide folded-cavity in-plane surface-emitting lasers

A 45 degrees angled reactive ion etching combined with an in situ monitoring technique was used to fabricate ridge waveguide folded-cavity in-plane surface-emitting lasers. This laser structure, with two 45 degrees C angle-etched internal total-reflection mirrors and an epitaxially grown distributed Bragg reflector, is very promising for OEIC applications. Laser-structure design and laser fabrication are addressed. A continuous-wave threshold current of 8 mA, the lowest reported in the literature, was achieved on 3- mu m-wide, 350- mu m long devices.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Low threshold current grating-coupled surface-emitting strained-InGaAs single quantum well laser with GaAs optical confinement structure

We have demonstrated low threshold current operation of a grating-coupled surface-emitting strained-InGaAs single quantum well laser with a distributed Bragg reflector. By considering the field discontinuity at the gain/grating section interface, our calculations show that the GaAs optical confinement structure can provide high effective reflectivity in the grating section. As a result, continuous wave threshold currents as small as 15 mA were attained at 22 °C, which is the lowest threshold current reported for a grating-coupled surface-emitting laser fabricated without epitaxial regrowth.

1.3 μm InGaAsP/InP multiquantum well buried heterostructure lasers grown by chemical-beam epitaxy

High performance InGaAsP/InP multiquantum well (MQW) buried heterostructure lasers emitting around 1.3 μm were prepared for the first time by chemical-beam epitaxy. At 20 °C, continuous-wave (cw) threshold currents were 5–8 mA and quantum efficiencies were 0.35–0.45 mW/mA for 250 μm long lasers having one facet ∼85% reflective coated. At 80 °C, the cw threshold currents remained low, 23 mA, quantum efficiency stayed high, 0.22 mW/mA, and output power of ∼10 mW was achieved. cw power output as high as 125 mW was achieved with 750 μm long lasers having AR–HR (∼5%–85%) coatings. Lasers with bulk active were also studied for comparison. Though they also have excellent device performance, in general, they are somewhat inferior to MQW lasers.

GaAlAs/GaAs single quantum well gain-coupled distributed feedback laser

A novel gain-coupled distributed feedback laser with a single quantum well (SQW) active layer is proposed and fabricated. The gain perturbation for the gain coupling is due to the periodically perturbed SQW active layer. The characteristics under continuous-wave (CW) operation are presented, included an excellent single-mode property and a very high yield in the single-mode oscillation. A CW threshold current of 31 mA and a high side-mode suppression ratio of 47 dB were achieved. The high single-mode-oscillation yield near 100% indicated the dominance of the gain-coupled optical feedback in the lasers.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Low-threshold, high-temperature pulsed operation of InGaAsP/InP vertical cavity surface emitting lasers

Room-temperature pulsed operation of InGaAsP (1.3 mu m)/InP vertical cavity surface emitting lasers has been achieved with threshold current as low as 50 mA using a constricted-mesa structure with dielectric mirrors. Above-room-temperature operation has also been realized with a maximum operation temperature of 66 degrees C. Pulsed and continuous-wave threshold currents at 77 K are 1.5 and 3.9 mA, respectively.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Strained multiple quantum well lasers emitting at 1.3 μm grown by low-pressure metalorganic vapor phase epitaxy

Low-threshold and high-output power of the first InGaAsP/InP graded index strained multiple quantum well lasers emitting near 1.3 μm wavelength is reported. A continuous wave threshold current of 10 mA and a quantum efficiency of 60% with maximum output power of 100 mW/facet is observed in uncoated lasers having compressively strained InGaAsP quantum wells. With high reflectivity on both facets, a reduced threshold current as low as 3.5 mA is observed. Highest output power of 250 mW was observed in lasers with antireflection-high reflection coating configuration operating at 10 °C. The improved performance of the lasers is attributed to both the reduced internal absorption loss (6 cm−1) and the suppressed nonradiative recombination in the structure.

The metal-organic vapour phase epitaxy growth of GaInAsP and GaAlInAs based graded refractive index separate confinement heterostructure multiple quantum well lasers incorporating linearly graded confinement layers

The epitaxial growth of long wavelength graded refractive index separate confinement heterostructure multiple quantum well (GRIN-SCH MQW) lasers by low pressure metal-organic vapour phase epitaxy is described. By varying the group III and group V gas flows simultaneously it was possible to produce GaInAsP material that was linearly graded between the solid phase compositions of InP and Ga0.18In0.82As0.40P0.60 (λ = 1.15 μm). This was achieved using experimental data for the growth of InP and GaInAsP at λ = 1.07 and 1.15 μm, together with a knowledge of the alloy composition vs. band gap relationship. The laser material was characterized by double-crystal X-ray diffraction using the (004) reflection (Δa/a = 580 ppm), photoluminescence spectroscopy (39 and 11 meV full width at half-maximum line-widths at 300 and 10 K respectively) and cross-section transmission electron microscopy (well and barrier thicknesses of 70 and 65 A respectively), which showed that the material was of high quality with compositionally abrupt heterointerfaces and precisely defined quantum wells. Auger electron and secondary ion mass spectrometry were used to confirm the grade linearity. High quality, linearly graded GaAlInA structures were also produced. Device results on GRIN-SCH MQW lasers are reported for which continuous wave threshold currents of 13.3 mA were obtained.

Deep-red continuous wave top-surface-emitting vertical-cavity AlGaAs superlattice lasers

Deep-red (770-nm) top-surface-emitting vertical-cavity AlGaAs lasers were fabricated and operated continuously at room temperature. An Al/sub 0.14/Ga/sub 0.86/As superlattice was used for an active-gain medium. Efficient current funneling was achieved by deep proton implantation. Continuous-wave (CW) threshold currents were 4.6 and 6.3 mA at 3.9- and 3.4-V bias for 10- and 15- mu m-diameter lasers, respectively. The maximum CW output power was >1.1 mW at room temperature without heat sink. Arrays of various top-surface-emitting lasers based on current funneling are expected to generate many applications for photonic switching, chip-to-chip communication, optical computing, and printing.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Molecular beam epitaxy-grown PbSnTe-PbEuSeTe buried heterostructure diode lasers

Buried heterostructure (BH) PbSnTe-PbEuSeTe lasers with a PbSnTe active layer were fabricated for the first time using a two-stage molecular beam epitaxy (MBE) growth procedure. Lasers with 4- mu m-wide and 0.65- mu m-thick buried Pb/sub 0.961/Sn/sub Sn0.039/Te active layer and Pb/sub 0.985/Eu/sub 0.015/Se/sub 0.02/Te/sub 0.98/ cladding layers were grown. Continuous wave (CW) operating temperature of 175 K was measured with CW threshold currents of 1.6 mA (20 K), 13.6 mA (80 K), and 195 mA (160 K). Single-mode operation with 3.0-cm/sup -1/-mode tuning was measured at 1639.8 cm/sup -1/ emission. >

Trapezoidal channeled substrate inner stripe phase-locked semiconductor laser arrays

A novel type of trapezoidal channeled substrate inner stripe diode laser array grown by single-step liquid-phase epitaxy was designed and fabricated. A six-element array with evanescent wave coupling, as well as leaky wave coupling, shows a continuous-wave threshold current of 170 mA and a pulsed peak power over 675 mW per facet without a coating. A clean single-lobe far-field pattern of beam width 2.4° is obtained.

High-power operation of a transverse-mode stabilised AlGaInp visible light (λ L = 683 nm) semiconductor laser

Continuous-wave (CW), stable fundamental-mode operation, up to 20 mW, was achieved with transverse-mode stabilised MOVPE-grown AlGaInP visible-light (λL = 683 nm) lasers. The CW threshold current was 67 mA and the external quantum efficiency was 41%. Up to 27 mW CW power was obtained from this laser diode.

Low-threshold, high-power zero-order lateral-mode DQW-SCH metal-clad ridge waveguide (AlGa)As/GaAs lasers

Metal-clad ridge waveguide (MCRW), double quantum well, separately confined heterostrucuture (DQW-SCH) lasers have been fabricated having continuous-wave (CW) threshold currents of 10–12 mA and external differential quantum efficiencies of 41–46% per uncoated facet. Light/current characteristics are linear to &gt;70 mW, and zero-order lateral mode operation was measured at 56 mW. The CW burn-off power density is nearly double the best previously reported value.

621 nm CW operation (0%C) of AlGaInP visible semiconductor lasers

Continuous-wave (CW) operation (0°C at 621 nm has been achieved for the first time by an AlGaInP mesa stripe laser, grown by metalorganic vapour-phase epitaxy. The lasing wavelength is shorter than the He-Ne gas laser's wavelength, 633 nm. The CW threshold current is 60 mA (4.8 kA/cm2).

Cw operation of 1.57-μm GaxIn1−xAsyP1−yInP distributed feedback lasers grown by low-pressure metalorganic chemical vapor deposition

Continuous wave operation of 1.57-μm distributed feedback lasers fabricated on material grown by two-step low-pressure metalorganic chemical vapor deposition growth process is reported for the first time. Room-temperature continuous wave threshold currents as low as 60 mA have been measured for devices with cavity length of 300 μm and stripe width of 5 μm. Single longitudinal mode operation at fixed mode was obtained under the continuous wave condition, in the temperature range 9–90 °C, with the wavelength shift of 0.9 Å/°C. A stop band of 25 Å in which no resonance mode emission existed, was observed in the output spectrum of the distributed feedback laser.

Room-temperature cw operation in the visible spectral range of 680–700 nm by AlGaAs double heterojunction lasers

Room-temperature cw operation at the wavelength below 700 nm has been achieved by AlGaAs double heterojunction (DH) lasers with a novel structure, in which a thick buffer layer is grown and the substrate is removed. Continuous-wave threshold currents were 60–120 mA in the visible spectral range of 680–700 nm. Also the fundamental transverse and single longitudinal mode were obtained under cw operation. The shortest cw wavelength is 683 nm at the present time.