David A. S. Loeber

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.

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.

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.

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.

Efficient and compact green laser for micro-projector applications

— Efficient and compact green lasers are keystone components for micro-projector applications in mobile devices. An architecture that consists of an infrared-producing DBR (distributed Bragg reflector) laser with a frequency-doubling crystal is used to synthesize a green laser that has high electrical-to-optical conversion efficiency and can be modulated at speeds required for scanner-based projectors. The design and performance of a green-laser package that uses adaptive optics to overcome the challenge of maintaining alignment between the waveguides of the DBR laser and the frequency-doubling crystal over temperature and lifetime is described. The adaptive optics technology that is employed uses the piezo-based smooth impact drive mechanism (SIDM) actuators that offer a very small step size and a range of travel adequate for the alignment operation. The laser is shown to be compact (0.7 cm3 in volume) and capable of a wall-plug efficiency approaching 10% (at 100-mW green power). It was demonstrated that the adaptive optics enables operation over a wide temperature range (10–60°C) and provides the capability for low-cost assembly of the device.

Compact and efficient green lasers for mobile projector applications

— Efficient and very-compact projectors embedded into mobile consumer-electronic devices, such as handsets, media players, gaming consoles, and GPS units, will enable new consumer use and industry business models. A keystone component for such projectors is a green laser that is commensurately efficient and compact. A synthetic green-laser architecture is described that can achieve efficiencies of 15%. The architecture consists of an infrared distributed Bragg reflector laser coupled into a second-harmonic-generation device for conversion to green.

63.2: Distinguished Paper: Efficient and Compact Green Laser Incorporating Adaptive Optics for Wide Operating Temperature Range

Green lasers with high efficiency are keystone components for mobile projectors. We demonstrate a miniature device (<0.7 cc volume) that utilizes adaptive optics for operation over a 50 °C temperature range without requiring a thermo-electric cooler. The use of adaptive optics also helps in reducing the cost of the laser assembly.

Impact of near-end residual reflectivity on the spectral performance of high-power pump lasers

Abnormal spectral characteristics are observed in high-power semiconductor pump laser modules with ultralow chip front-facet reflectivity levels. We have identified the root cause as destructive interference in an external-cavity reflection from an antireflection (AR) coated fiber tip. This suppressive external cavity imposes a practical limit on the lower desirable bound for front-facet AR coatings for high-power lasers and uncooled fiber Bragg grating stabilized semiconductor devices.

P-233: Multimode DBR Laser Operation for Frequency Doubled Green Lasers in Projection Displays

In frequency doubled green lasers for laser scanning micro projectors, the wavelength fluctuations can create low spatial frequency and repeatable image artifacts that significantly degrade the image quality. We demonstrate a technique where the laser gain current is repeatedly reset to zero and the laser phase is randomized, both at high frequency. The image defects are replaced by high spatial frequency content noise that minimizes the detrimental effects in the human vision system.

Polarization extinction ratio impact on spectral stability of Bragg grating stabilized laser diodes

We demonstrate that polarization extinction ratio (PER) affects the spectral instability of 980-nm band fiber Bragg grating stabilized pump lasers using a polarization-maintaining fiber pigtail. Enhanced spectral stability better than 0.01 nm is demonstrated in devices with superior PER.