Failure Analysis using Optical Evaluation Technique (OBIC) of LDs for Fiber Optical Communication
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1195-B01-02
Failure Analysis using Optical Evaluation Technique (OBIC) of LDs for Fiber Optical Communication Tatsuya Takeshita1 and Hiromi Oohashi1 NTT Photonics Laboratories, NTT Corporation, 3-1, Morinosato Wakamiya, Atsugi, Kanagawa, 243-0198, Japan
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ABSTRACT We have analyzed lasers suffering from sudden and wear-out failure by employing the optical beam induced current (OBIC) measurement technique. The OBIC technique is used with lights at several wavelengths to detect the degradation region and estimate the degradation degree. We found that defects around the antireflection (AR) facet govern both the long-term stability and the catastrophic optical damage (COD) level for a laser exhibiting sudden failure. In addition, for a laser exhibiting wear-out failure, certain defects diffuse from the separate confinement heterostructure (SCH) layer to the active layer, and the degradation region is confirmed to be located in the active layer but not in the vicinity of the AR facet. INTRODUCTION The introduction of high-speed services for fiber-optic access subscribers has led to a huge growth in data traffic. The rapid diversification of services means that next generation networks must be built quickly, economically and reliably [1]. These systems are supported by high performance devices. A laser that can operate at high temperature [2],[3] allows us to eliminate the thermo-electric cooler conventionally needed in a transmitter module, which results in reductions in cost, power consumption and size. Moreover, a high-power laser provides a wide tolerance when we couple it with optical fibers. In addition, a high-power pump laser [4],[5] is needed to realize a wide-band and high-power erbium-doped fiber amplifier. This makes high-performance laser chips one of the keys to achieving highly reliable and cost-effective systems. It is well known that severe conditions reduce the lifetime of a laser [6]. In terms of laser reliability, we must clarify the degradation mechanism and postpone or suppress degradation if we are to achieve a reliable high-performance laser. Optical-beam-induced current (OBIC) measurement [7]-[10], as well as other approaches, such as electron-beam-induced current (EBIC) measurement [11], and luminescence measurement [12], can determine the existence of deterioration in optoelectronic devices. We have analyzed degraded lasers using the OBIC technique. This technique has the advantages of being non-destructive and highly sensitive [13]. In addition, it provides high spatial resolution in degradation analyses. When there are nonradiative recombination centers in the degraded region, the OBIC intensity decreases as the recombination density increases [14]. The OBIC is measured through the window of a transistor outline (TO) can before and after aging. By using the same LDs we can detect an OBIC change for several aging times, and clarify the degraded regions. In addition, we can estimate the relative OBIC intensity prior to aging, which is useful for analyzing the degree of laser degradation.
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