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coated with positive-type photoresist (AZ-1350) and exposed[23] T. Kobayashi, T. Kawakami, and Y. Furukawa, ''Thermal diagnoto mercury light for 1 minute after prebaking at 90°C for 20 sis of dark lines in degraded GaAs-AlGaAs double-heterostructure minutes. Then, the lasers were operated at 20"C, 5 mW/facet for lasers," Japan. J. Appl. Phys., vol. 14, pp. 508-515, Apr. 1975. 20 minutes. After this, they were syringed in the acetone solution, with ultrasonic vibration, for 3 minutes. The photoresists coated on three lasers were completely dissolved, but in two lasers, no matter what, only part of the photoresist coated at the emitting area could not be dissolved. Note that remaining photoresist was observed on either, but not both, mirrors of the laser. The actinic absorbance of the photoresist decays suddenly in light with a wavelength above 0.5 pm, so 0.8 pm radiation from a laser is transparent to the photoresist. We have certified that photoresist baked at 150°C for 20 minutes could be dissolved completely in the acetone solution, but not 180°C for 20 minutes. Thus, we concluded that a temperature rise of about 150°C did take place at the mirror surface at least in two lasers. Similar results have been presented by 0. Matsuda et al. at the 26th Nat.Conv. Japan. SOC. Appl. Phys., Spring 1979 (in Japanese). Y. Nannichi, J. Matsui, and K. Ishida, "Rapid degradation in double-heterostructue lasers-11: Semiquantitative analyses on the propagation of dark line defects," Japan. J. Appl. Phys., vol. 14, pp. 1561vol. 14, pp. -1568vol. 14, pp. , Oct. 1975. Influence of Optical Feedback on Laser Frequency Spectrum and Threshold ConditionsJENS HENRIK OSMUNDSEN AND NIELS GADE Abstruct-The steady state behavior of the external cavity operated laser has been analyzed, taking into account multiple reflections.The effect of optical feedback is included in the phase and gainconditions by a factor which is shown to have a simple geometrical representation. From this representation it is easily seen how the laser frequency spectrum and the threshold gain depend on external parameters such as distance to the reflection point and the amount of optical feedback.Furthermore, by inserting a variable attenuator in the external cavity and measuring the threshold current versus transmittance we have simultaneously determined the photon lifetime and the absolute amount of optical feedback. For the laser considered we found the photon life-

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Performance-related effects of system level temperature changes can be a key consideration in the design of many types of optical instruments. This is especially true for space-based imagers, which may require complex thermal control systems to maintain alignment of the optical components. Structural-Thermal-Optical-Performance (STOP) analysis is a multi-disciplinary process that can be used to assess the performance of these optical systems when subjected to the expected design environment. This type of analysis can be very time consuming, which makes it difficult to use as a trade study tool early in the project life cycle. In many cases, only one or two iterations can be performed over the course of a project. This limits the design space to best practices since it may be too difficult, or take too long, to test new concepts analytically. In order to overcome this challenge, automation, and a standard procedure for performing these studies is essential. A methodology was developed within the framework of the Comet software tool that captures the basic inputs, outputs, and processes used in most STOP analyses. This resulted in a generic, reusable analysis template that can be used for design trades for a variety of optical systems. The template captures much of the upfront setup such as meshing, boundary conditions, data transfer, naming conventions, and post-processing, and therefore saves time for each subsequent project. A description of the methodology and the analysis template is presented, and results are described for a simple telescope optical system.

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SummaryAn automatic linewidth control loop which provides stable optimum linewidth reduction and single cavity mode operation of an external cavity semiconductor laser is presented. Stable linewidth reduction from 70 MHz to below 2 MHz is obtained for a 1.3 μm BH-laser, whereas simultaneous mean frequency stabilization to within 1 kHz and linewidth reduction from 17 MHz to 1.6 MHz is demonstrated for an 830 nm CSP-laser.