Martin H. Hu

Thermal management strategies for high power semiconductor pump lasers

Semiconductor pump lasers are an important component in Erbium-doped fiber amplifiers and Raman amplifiers. Thermal management has become one of the major obstacles of pump laser development. Understanding of the thermal behavior of high power laser packages is crucial to the thermal design and optimization of pump lasers. In this paper, we report on the thermal characteristics of a high power pump laser and discuss the issues associated with heat dissipation. The thermal management of high power pump laser modules mainly consists of three aspects. One is the thermal resistance reduction which reduces bulk temperature rise in the laser diode chip. The second is facet temperature control and the third is the thermoelectric cooler (TEC) coefficient of performance improvement. In this paper, the approaches to reduce thermal resistance and facet temperature at the chip level and package level will be reviewed and the thermal design and optimization of the package assembly to improve the TEC coefficient of performance will be discussed.

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

Highly reliable high-power 980-nm pump laser

We report on highly reliable, high-power, and high-performance 980-nm quantum-well laser chips and modules. Ridge waveguide laser diode chips with 750-mW output power and 500-mW fiber Bragg grating stabilized modules have been achieved and Telcordia-qualified. Long-term reliability tests show a very low failure rate of 400 FIT (failures in time) at 900-mA operating current or 500-mW module power. The kink-free fiber coupled module output power can be as high as 640 mW with grating stabilization, which produces very good wavelength stability and power stability. A further improved structure shows a record continuous-wave rollover chip power of 1.6 W for the 5-/spl mu/m-wide ridge waveguide laser diodes.

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-performance 980-nm ridge waveguide lasers with a nearly circular beam

We report high-performance 980-nm ridge waveguide quantum-well lasers with extremely low vertical beam divergence of 13/spl deg/. A very small aspect ratio of 1.6 is obtained at high operating power of 900 mW. In addition to the more circular beam, low threshold, high efficiency, high characteristic temperature, and high output power of over 1.18 W are achieved. The fiber coupled output power can be as high as 680 mW with fiber Bragg grating stabilization. Excellent wavelength and power stability are also demonstrated.

10-Gb/s error-free transmission under optical reflection using isolator-free 1.3- /spl mu/m InP-based vertical-cavity surface-emitting lasers

Error-free transmission through 10-km single-mode fiber at 10 Gb/s under -13-dB optical reflections has been demonstrated for the first time using a directly modulated 1.3-/spl mu/m InP-based VCSEL without any optical isolator. The 13-GHz relaxation oscillation frequency and stable polarization suppresses relative intensity noise degradation under optical reflection. Only 1-dB error-free power penalty has been observed with optical reflection set with the worst polarization direction.

Design, performance, and reliability of 980 nm pump lasers

This paper extensively studies the design and resulting performance of high power EDFA pump lasers to increase the operating power with each generation of chip developed while maintaining or improving other critical design features.

Design and implementation of metallization structures for epi-down bonded high power semiconductor lasers

High power semiconductor lasers have found increasing applications in industrial, military, commercial and consumer products. The thermal management of high power lasers is critical since the junction temperature rise resulting from large heat fluxes strongly affects the device characteristics, such as wavelength, kink power, threshold current and efficiency, and reliability. The epitaxial-side metallization structure of epi-down bonded lasers has significant impact on the thermal performance and reliability of the high power semiconductor lasers. In this paper, the influence of the epitaxial-side metal (p-metal) on the thermal behavior of a GaAs-based high power single-mode laser, mounted epi-side down, is studied using finite element analysis. Metallization structures having different diffusion barriers for eutectic AuSn solder are designed and implemented, and the metallurgical stability of the four metal systems, Ti/Pt/thick Au (2-3 /spl mu/m thick), Ti/Pt/thick Au/Ti/Pt/Au, Ti/Pt/thick Au/Ti/Ni/Au, and Ti/Pt/thick Au/Ti/Cr/Au, are reported.