Μm Cavity Length Research Articles

Optically pumped GaN/Al0.1Ga0.9N double-heterostructure ultraviolet laser

Molecular-beam epitaxy was used to grow a 100 nm Al0.1Ga0.9N/100 nm GaN/500 nm Al0.1Ga0.9N double heterostructure on a 10-μm-thick GaN buffer layer grown with hydride vapor phase epitaxy on (0001) sapphire. Lasing from the 100 nm GaN active layer has been obtained at ∼359 nm at liquid-nitrogen temperature (77 K) and at ∼365 nm at room temperature (295 K), using transverse optical pumping at 337.1 nm with a 600 ps transversely excited atmospheric pressure pulsed nitrogen laser. Threshold pump fluences were measured to be 0.3 and 0.5 mJ/cm2 at 77 and 295 K, respectively, for a laser with 65 μm cavity length. In a laser of 23 μm cavity length, longitudinal cavity modes were observed with 0.56 nm spacing, corresponding to a group refractive index of 5.0 at the lasing wavelength.

Low-threshold pulsed operation of long-wavelengthlasers on Sifabricated by direct bonding

Low-threshold room-temperature pulsed operation of InGaAs/InGaAsP multiquantum-well (MQW) lasers (λ ≃ 1.55 µm) on Si substrates is demonstrated. These laser structures were first grown on InP substrates, then bonded at 700°C onto Si substrates with buffer layers. The mesa-stripe broad-area lasers have a threshold current density of 1.7 kA/cm2 (50 µm mesa width, 330 µm cavity length), which is comparable to the value for lasers on InP substrates.

Microwave characterization of corner reflector p-doped multiple quantum-well lasers

We report on the dc and microwave characterization of p-doped multiple quantum-well strained layer lasers with single-ended output provided by the use of a total-internal-reflector corner facet formed with chemically assisted ion beam etching. Mesa geometry devices suitable for on-wafer microwave probing with 150 μm cavity lengths have threshold currents of 12 mA and bandwidths of 20 GHz. Damping rates as a function of the square of resonance for corner reflector (CR) devices and standard devices with two plane mirrors mere compared, showing that the high speed characteristics of CR devices were quite similar to standard devices. Simplicity in processing and single-sided output makes these lasers ideal candidates for efficient, broad bandwidth optical sources suitable for monolithic integration into OEICs.

Chemical beam epitaxy growth of 1.3 μm InGaAsP/InP double heterostructure lasers using all gas source doping

Low threshold 1.3 μm InGaAsP/InP double heterostructure lasers were fabricated using all gas source chemical beam epitaxy (CBE). Gas source doping of n- and p-type InP and InGaAs was successfully achieved using tetraethyltin and diethylzinc. The minimum threshold current density (Jth) for a 1800 μm cavity length laser was 680 A/cm−2. This is lowest Jth value reported for CBE grown double heterostructure lasers at 1.3 μm. These lasers exhibited an internal quantum efficiency (ηi) and internal loss (αi) of 51% and 16 cm−1, respectively. The temperature dependence of the threshold current is described by a single exponential T0 of 51 K.

High power single mode operation of AlGaInP visible laser diode with lateral leaky waveguide structure

AlGaInP visible laser diode with lateral leaky waveguide structure employing 0.025 of negative refractive index step have been fabricated. In comparison to conventional loss guided structure, lateral leaky waveguide structure indicated stable fundamental mode operation. The output power at kink for lateral leaky waveguide laser was around 1.5 times higher than loss guided structure for same stripe widths. The stability was attributed to large mode discrimination against higher order mode. The lateral leaky waveguide laser with 560 μm cavity length employing the antireflection (5%)/high reflection (82%) showed 66 mW of output power with no kinks at 25/spl deg/C.

Transmission-line delay limitations of laser bandwidths

The paper describes the constraints placed on modulation bandwidths of horizontal cavity semiconductor lasers by the dissipative and dispersive effects due to the transmission of electric signals along a narrow injection stripe. The calculations employ a distributed transmission-line model where the incremental small-signal laser equivalent circuit incorporates the effects of photon-carrier interactions represented in relaxation oscillations. At 150 µm cavity length, such as those feasible in strained quantum-well structures, the bandwidths appear to be limited to approximately 30 GHz even under the most idealised conditions. It is suggested that further improvements in bandwidths will require a judicious design of the laser travelling-wave structure. Vertical cavity laser structures may offer an alternative approach to increasing the bandwidth.

Temperature Dependence of Threshold Current of Transverse Single-Mode InGaAsP/InGaP Buried-Heterostructure Laser

Separate-confinement-heterostructure single-quantum-well (SCH-SQW) InGaAsP/InGaP structures were grown on a (100) GaAs substrate by liquid-phase epitaxy (LPE) and then buried-heterostructure (BH) lasers were fabricated after mesa etching. The output power of laser diodes could be cw-operated near 50 mW without any kink in the transverse single mode. The measured values of a charateristic temperature T0 for BH InGaAsP/InGaP lasers were around 100 K for ∼500 µm cavity length. This relatively low value compared to the AlGaAs/GaAs quantum-well lasers could be better explained in terms of carrier leakage over the heterojunction barrier rather than Auger recombination which is intrinsic to quaternary semiconductor materials.

Buried heterostructure laser diodes fabricated using in situ processing

An in situ process which includes electron cyclotron resonance plasma etching and molecular beam epitaxial regrowth is applied to the fabrication of buried heterostructure vertical cavity surface-emitting laser (SEL) diodes and edge-emitting laser (EEL) diodes. The buried SEL with a 7.5 μm diameter has a pulsed laser threshold current of 1 mA, and a threshold voltage of 4 V with a peak power of 0.9 mW. The buried EEL with 2.5 μm stripe width and 800 μm cavity length has a threshold current density of 500 A/cm2.

GaInAsP/InP 1.35 μm double heterostructure laser grown on silicon substrate by metalorganic chemical vapor deposition

A 1.35 μm GaInAsP/InP double heterostructure laser has been grown on a Si substrate using low-pressure metalorganic chemical vapor deposition. This was done without the use of a superlattice layer or a very thick InP buffer layer, which are used to prevent the dislocations from spreading into the active layer. Pulsed operation with output power of over 200 mW per facet was achieved at room temperature for broad area lasers with 20 μm width and 170 μm cavity length. The threshold current density of a 350 μm cavity length device was 9.8 kA/cm2. The characteristic temperature was 66 K.

High performance strained InGaAs/AlGaAs buried-heterostructure quantum-well lasers fabricated by in situ etching and regrowth

We report a novel method for growth and fabrication of high performance strained InGaAs/AlGaAs quantum-well buried-heterostructure (BH) lasers. The method involves growth of the laser structure by molecular beam epitaxy, mesa formation by in situ melt etching using SiO2 stripes as a mask, and regrowth of p−-p-n AlGaAs isolating layers by liquid phase epitaxy. The method allows etching, preservation of high quality sidewalls, regrowth, and planarization in one step with negligible thermal disordering. Compared to ridge waveguide lasers, the BH lasers so fabricated have significantly lower threshold current, higher power output, higher temperature operation, lower cavity losses, and kink-free light-current (L-I) characteristics, as expected. A cw power of 150 mW/facet at 986 nm was measured from a 400-μm-long BH laser with 11 μm active stripe width. A minimum threshold current of 2.5 mA was measured for lasers with 3.0 μm active width and 300–400 μm cavity length. The L-I characteristics of 500-, 800-, and 1300-μm-long lasers with 3.0 μm active width were linear up to the currents corresponding to a current density of 10 kA cm−2. At higher current densities, a sublinear increase of power with current was observed. Stable fundamental transverse mode operation was obtained up to 100 mW emitted power.

High power, 0.98 μm, Ga0.8In0.2As/GaAs/Ga0.51In0.49P multiple quantum well laser

We report the fabrication of high quality Ga0.8In0.2As/GaAs/Ga0.51In0.49P multiple quantum well laser emitting at 0.98 μm grown by low pressure metalorganic chemical vapor deposition. Continuous wave operation with output power of 500 mW per facet was achieved at room temperature for a broad area laser with 130 μm width and 300 μm cavity length. This is an unusually high value of output power for this wavelength laser in this material system. The differential quantum efficiency exceeded 75% with excellent homogeneity and uniformity. The characteristic temperature, T0 was in the range of 120–130 K.

Strained-layer InGaAs quantum well lasers emitting at 1.5 μm grown by chemical beam epitaxy

Laser characteristics of double channel planar buried heterostructure lasers with InxGa1−xAs/InGaAsP multiquantum wells (MQW) fabricated by a combination of chemical beam epitaxy and liquid phase epitaxy are described for the InAs content x of the InxGa1−xAs ranging from 0.53 to 0.71. There is no discernible difference in the minority carrier lifetime of the unstrained and strained MQWs. All the lasers have almost the same threshold current of 15±1 mA. Characteristic temperature T0 is improved in the strained lasers; the laser with x=0.62 has a T0 of as high as 98 K at 900 μm cavity length. Resonance oscillation frequency fr increases with the InAs content, i.e., the amount of the compressive strain.

Reliable high-power (40 mW) operation of transverse-mode stabilised InGaAlP laser diodes with strained active layer

Reliable high-power operation of transverse-mode stabilised InGaAlP laser diodes has been achieved by using a selectively-buried-ridge waveguide structure with a very thin (150 A) active layer. A strained In0.62Ga0.38P active layer and a 800 μm cavity length were employed to reduce the operation current density at high-power and high-temperature operation. A highly reliable operation for over 2000 h has been achieved with a 40 mW output at 40°C. The lifetime of the lasers was limited by the operation current density.

Room-temperature operation of an InGaAsP double-heterostructure laser emitting at 1.55 μm on a Si substrate

The room-temperature operations of an InGaAsP double-heterostructure (DH) laser emitting at 1.55 μm on a Si substrate is reported. A pulsed threshold current as low as 46 mA has been measured for a ridge waveguide laser with a 4 μm strip width and a 200 μm cavity length. This successful laser operation is due to the high crystalline quality of the DH structure with full width at half maximum of x-ray rocking curves as low as 110 arcsec grown on a Si substrate by the organometallic vapor phase epitaxy/vapor mixing epitaxy hybrid method. A correlation between the optical property of an InGaAsP DH and its crystalline quality is also discussed.

Long-lived dry-etched AlGaAs/GaAs ridge waveguide laser diodes

Chemically assisted ion beam etching has been utilized to fabricate ridge waveguide GaAs/AlGaAs lasers which are as reliable, if not more so, than their oxide stripe counterparts. Results on 60- and 5-μm-wide ridge waveguide lasers with 600 μm cavity lengths as compared to oxide stripe lasers with the same configuration are reviewed and multikilohour lifetimes are demonstrated.

Heteroepitaxy of Inp on Si for Optical Devices

ABSTRACTIn situ measurements of dislocations at growth temperature have been made on the heteroepitaxial systems of GaAs/Si and GaP/Si. It was found that the etch pit densities of heteroepitaxial layers were as low as those of bulk wafers at the growth temperature and increase to 107 cm−2 when the layers cool down to room temperature. This means that the thermal stress determines the quality of heteroepitaxial layers.The InP on Si system, in which the thermal expansion coefficient difference is smaller than other heteroepitaxial systems, has been studied. High quality InP has been obtained using a GaAs buffer layer, strained-layer superlattice insertion, and thermal cycle annealing and regrowth. Full width at half maximum of X-ray rocking curve was 110" at 13 µ thickness.An InGaAsP laser diode emitting at 1.55 µm was successfully made on Si. The threshold current was 46 mA at room temperature for a ridge waveguide laser with a 4 µm width and a 200,µm cavity length.

1.5 µm GaInAs/GaInAsP graded index separate confinement heterostructure multiple quantum well (GRINSCH-MQW) laser diodes grown by metalorganic chemical vapour deposition (MOCVD)

Very low threshold current density GaInAs/GaInAsP GRINSCH-MQW laser diodes grown by MOCVD emitting at 1.5 µm are demonstrated for the first time. The average threshold current density for 375 µm cavity length devices (200 µm width) was 1.2 kA/cm2, which is the lowest value reported for GaInAs/InP laser diodes.

Performance of 1.5 µ λ/4-shifted DFB-SIPBH laser diodes with electron beam defined and reactive ion-etched gratings

1.5µm λ/4-shifted DFB-SIPBH laser diodes were made with electron-beam-defined and reactive ion etched gratings. The surface damage created by the reactive ion etching has no adverse effect on the device performances. The resultant devices with a 254 µm cavity length had a minimum linewidth of 3 MHz and a 3 dB modulation bandwidth of 7 GHz.

First GaInAsP-InP double-heterostructure laser emitting at 1.27 μm on a silicon substrate

We report the first successful room-temperature GaInAsP-InP double-heterostructure laser emitting at 1.27 μm, grown by low-pressure metalorganic chemical vapor deposition on a Si substrate. A pulsed threshold current density of 10 kA/cm2 at room temperature with an external quantum efficiency of 10% per facet and an output power of 20 mW (for an oxide-defined stripe geometry with 12 μm stripe width and 250 μm cavity length) has been measured. The first aging test in pulse operation shows an increase of threshold current of only 7% for a cumulative time of 80 s at room temperature.

CW operation of 1.5 μm InGaAsP/InP BH lasers with a reactive-ion-etched facet

The reactive-ion-etching (RIE) technique utilising a TiO2 mask and Cl2-Ar gas is successfully applied to facet mirror fabrication of 1.5 μm InGaAsP/InP buried-heterostructure (BH) lasers. Room-temperature CW operation has been achieved with a structure having one etched and one cleaved facet. A threshold current value of 30 mA at 25°C has been achieved for a laser with a 380 μm cavity length.