Stable Single-mode 20-channel Uniform Buried Grating DFB QCL Array Emitting at ~8.3 μm

A 20-channel distributed feedback (DFB) quantum cascade laser (QCL) arrays based on uniform buried grating have been demonstrated. In pulsed mode, peak power reaches 80 mW and slope efficiency reaches 167 mW/A for 2.5-mm-long laser in the arrays at room temperature. The loss difference of two band-edge mode increases when reflectivity of the front facet becomes small, which prevents the mode hopping. The device shows linear tuning after the anti-reflectivity coating is deposited in the front facet, maintaining peak power of 64 mW. The whole chip covers a tuning range of 64 cm-1, centering at 8.3 μm, with side-mode-suppression-ratio over 20 dB at room temperature.

Nondestructive Measurement for Front Facet Temperature of Semiconductor Lasers

A convenient, simple method is proposed to measure the front facet temperature, which is the highest temperature in the semiconductor laser diode (LD), of a GaAs-based laser by employing thermoreflectance technique. Using an optical system featured in fiber connection, we measured the facet reflectivity of the 808-nm AlGaInAs/AlGaAs LD, which gives information about the temperature of the output facet. The fiber system operates at the wavelength of 1550 nm which avoids the absorption of the probe beam by the tested LD and consists of a fiber-coupled 1550 nm laser illuminant and photodiode. All optical elements in the system are connected by the fibers. The current signal collected from the photodiode is related to the facet reflectivity and represents facet temperature. We compared the facet temperatures determined by thermoreflectance technique with the cavity temperature obtained by forward-voltage method and found that the former is as much as three times as the latter.

Effective Failure Analysis for Packaged Semiconductor Lasers with a Simple Sample Preparation and Home-Made PEM System

As the application requirements of semiconductor lasers continue to increase, severe challenges are brought to the reliability of semiconductor lasers. In order to promote the study of laser failure, this paper proposes an effective failure analysis method for packaged semiconductor lasers with a simple sample preparation and home-made photon emission microscopy (PEM) system. The new simple sample preparation process for failure analysis is presented and the necessary polishing fixture is designed so that sample can be obtained without expensive and complex micro-/nano-processing. Two types of home-made PEM experimental systems were established for observing the failure from the front facet and active region of semiconductor lasers. Experimental results showed that, with the proposed sample preparation flow, the home-made PEM experimental system effectively observed the leakage defects from the front facet and dark spot defects (DSDs) in the active region of semiconductor lasers. The method can help researchers and laser manufactures to perform effective failure analysis of packaged semiconductor lasers.

Spectral Linewidth vs. Front Facet Reflectivity of 780 nm DFB Diode Lasers at High Optical Output Power

The influence of the front facet reflectivity on the spectral linewidth of high power DFB (distributed feedback) diode lasers emitting at 780 nm has been investigated theoretically and experimentally. Characterization of lasers at various front facet reflections showed substantial reduction of the linewidth. This behavior is in reasonable agreement with simulation results. A minimum linewidth of 8 kHz was achieved at an output power of 85 mW with the laser featuring a front facet reflectivity of 30%. The device with a front facet reflectivity of 5% reached the same linewidth value at an output power of 290 mW.