Hong Ky Nguyen

Comparison between epi-down and epi-up bonded high-power single-mode 980-nm semiconductor lasers

Epi-down and epi-up bonded high-power single-mode 980-nm lasers have been studied in terms of bonding process, thermal behavior, optical performances, and long-term laser reliability. We demonstrated that epi-down bonding can offer lower thermal resistance and improved optical performance without degrading the long-term laser reliability. An optical power of 630 mW was obtained for the first time from an epi-down bonded 980-nm pump module. Our studies have shown that epi-down bonding of single-mode 980-nm lasers can reduce junction temperature and thermal resistance by up to 30%. Experimental measurements showed over 20% in thermal rollover power improvement and over 25% reduction in wavelength shift versus current in epi-down mounted lasers compared to epi-up mounted lasers. Lifetime test over 14 000 h at 500 mA and 80/spl deg/C of the epi-down bonded lasers is reported for the first time.

107-mW low-noise green-light emission by frequency doubling of a reliable 1060-nm DFB semiconductor laser diode

We have generated 107-mW green-light emission by frequency doubling of a reliable 1060-nm distributed feedback (DFB) laser diode using a periodically poled MgO-doped lithium niobate waveguide in the most compact single-pass configuration. The green power variation is lower than 1% at frequencies below 82 kHz. The relative intensity noise of -150 dB/Hz has been measured at 100 MHz. We also report 5000-h life-test results of 1060-nm DFB lasers at 80/spl deg/C.

High-power high-Modulation-speed 1060-nm DBR lasers for Green-light emission

We report on the static and dynamic performance of high-power and high-modulation-speed 1060-nm distributed Bragg reflector (DBR) lasers for green-light emission by second-harmonic generation. Single-wavelength power of 387 mW at 1060-nm wavelength and green power as high as 99.5 mW were achieved. A thermally induced wavelength tuning of 2.4 nm and a carrier-induced wavelength tuning of -0.85 nm were obtained by injecting current into the DBR section. Measured rise-fall times of 0.2 ns for direct intensity modulation and 0.6 ns for wavelength modulation make the lasers suitable for >50-MHz green-light modulation applications

304 mW green light emission by frequency doubling of a high-power 1060-nm DBR semiconductor laser diode

We report for the first time, to the best of our knowledge, 304 mW green light emission generated by frequency doubling of the output from a 1060-nm DBR semiconductor laser using a periodically poled MgO-doped lithium niobate waveguide in a compact single-pass configuration. The excellent performance of these DBR lasers, including a kink-free power greater than 750 mW, single-spatial-mode output beam, single-wavelength emission spectra, and high wavelength-tuning efficiency, plays an important role in the generation of high-power green light.

High power 1060-nm raised-ridge strained single-quantum-well lasers

We report a high kink-free facet power of 852 mW and a high single-wavelength facet power of 350 mW for 1060-nm raised-ridge Fabry-Perot (FP) and distributed-feedback (DFB) lasers, respectively.

High-power distributed Bragg reflector lasers for green-light generation

We report on the design, fabrication and performance of high-power and high-modulation-speed 1060-nm DBR lasers for green-light emission by second harmonic generation. Single-spatial-mode and single-wavelength power more than 450 mW of 1060-nm wavelength was achieved with a 3-section DBR laser with non-absorbing DBR and phase sections created by an impurity-free quantum-well intermixing technique. A thermally-induced wavelength tuning of 2.4 nm and a carrier-induced wavelength tuning of -0.85 nm were obtained by injecting current into the DBR section. The green power as high as 104.6 mW was demonstrated by coupling the DBR laser output to a second-harmonic-generation waveguide. Measured rise/fall times of 0.2 ns for direct intensity modulation and 0.6 ns for wavelength modulation make the DBR lasers suitable for >=50-MHz green-light-modulation applications. The detrimental thermally-induced patterning effect and a differential-phase modulation scheme as a solution are discussed.

Grating stabilization design for high-power 980-nm semiconductor pump lasers

Wavelength stabilization of high-power pump lasers for fiber amplifier applications involves complex interactions between the laser chip and the fiber Bragg grating (FBG). We present a comprehensive theoretical model for the window of operation in the coherence collapse (CC) regime while maintaining wavelength locking in 980-nm FBG-stabilized pumps. Experimental data from the development of a 500-mW grating stabilized pump verifies the theory. We also provide the first evidence that the critical feedback distance for CC operation of longer laser diode chips is sensitive to detuning.

Reliability and qualification of high-power wavelength-tunable 1060-nm laser diode for ultra-compact laser projector application

We report highly reliable 1060-nm DBR semiconductor lasers after aging the gain section and DBR-section heater for up to 24000 and 11000 hrs, respectively, at various high-stress conditions.

Reliability of High-Power 1060-nm DBR Lasers

We report highly reliable 1060-nm DBR lasers with a single-wavelength output power larger than 350 mW and a failure rate as low as 3.2 kFITs at a heat-sink temperature of 25degC and a gain current of 500 mA. The reliability data of the high-power 1060-nm DBR lasers under longest aging tests at the highest level of current and temperature stress have been obtained for the first time, to the best of our knowledge

1.3-1.5 μm quantum dot lasers on foreign substrates: growth using defect reduction technique, high-power CW operation, and degradation resistance

We have performed a systematic study of structural and optical properties of Quantum dot (QDs) lasers based on InAs/InGaAs quantum dots grown on GaAs substrates emitting in the 1.3 - 1.5 μm range. 1.3 μm range QD lasers are grown using GaAs as matrix material. It is shown that the lasers, grown with large number of QD stacks are metamorphic, with plastic relaxation occurring through the formation of misfit dislocations. Thus, 1.3 μm QD lasers with large number of stacks grown without strain compensation are metamorphic. Another type of defects is related to local dislocated clusters, which are the most dangerous. When proper optimization of the growth conditions is carried out, including a selective thermal etching off of statistically formed dislocated clusters through the defect-reduction technique (DRT), no significant impact of misfit dislocations on the degradation robustness is observed. In uncoated devices a high cw single mode power of ~700 mW is realized limited by thermal roll-over, which is not affected by 500 h ageing at room temperature. At elevated temperatures the main degradation mechanism revealed is catastrophic optical mirror damage (COMD). When the facet are passivated, the devices show the extrapolated operation lifetime in excess of 106 h at 40°C at ~100 mW cw single mode output power. Longer wavelength (1.4 - 1.5 μm) devices are grown on metamorphic (In,Ga,Al)As layers deposited on GaAs substrates. In this case, the plastic relaxation occurs through formation of both misfit and threading dislocations. The latter kill the device performance. Using DRT in this case enables blocking of threading dislocation with growth of QDs in defect-free upper layers. DRT is realized by selective capping of the defect-free areas and high-temperature etching of nano-holes at the non-capped regions near the dislocation. The procedure results in etching of holes and is followed by fast lateral overgrowth with merger of the growth fronts. If the defect does not propagate into the upper layer when the hole is capped, the upper layers become defect-free. Lasers based on this approach exhibited emission wavelength in the 1.4 -1.5 μm range with a differential quantum efficiency of about ~50%. The narrow-stripe lasers operate in a single transverse mode and withstand continuous current density above 20 kA cm-2 without degradation. A maximum continuous-wave output power of 220 mW limited by thermal roll-over is obtained. No beam filamentation was observed up to the highest pumping levels. Narrow stripe devices with as-cleaved facets are tested for 60°C (800 h) and 70°C (200 h) on-chip temperature. No noticeable degradation has been observed at 50 mW cw single mode output power. This shows the possibility of degradation-robust devices on foreign substrates. The technology opens a way for integration of various III-V materials and may target degradation-free lasers on silicon for further convergence of computing and communications.