The use of optical beam induced current (OBIC) and photoluminescence (PL) imaging is a valuable tool for failure analysis of laser diodes. Examples of applications to three different types of lasers demonstrate the effectiveness of the approach and the high resolution attainable. Differences with the more popular SEM techniques are also discussed.
Multi-emitter laser devices, stacked to form 2-dimensional arrays, have been shown to effectively pump Nd:YAG slabs in solid state laser systems. Using these arrays as substitutes for flashlamps provides the potential for increased reliability of laser systems. However, to quantify this reliability improvement, laser arrays must be life tested. To ensure that the life test data accurately describes the array lifetimes, the life test system must possess the following characteristics: adequate control of operating stresses, to ensure that the test results apply to true use-conditions; continuous monitoring and recording of array health, to capture unpredictable variations in array performance; in-situ parameter measurement, to measure array performance without inducing handling damage; and extensive safety interlocks, to protect personnel from laser hazards. This paper describes an array life test system possessing these characteristics. It describes the system hardware, operating and test software, and the methodology behind the system's use. We demonstrate the system's performance by life testing 2-dimensional laser arrays having previously documented front facet anomalies. Disadvantages as well as advantages of design decisions are discussed.
The asymmetries induced by optical feedback in semiconductor laser diodes inserted in optical systems provides a possible way of noninvasive monitoring laser dynamics and system properties. A method, based on a microscopic model for single-mode laser diodes with additional terms to describe optical feedback contribution, is proposed.
Application of semiconductor lasers in fiber-in-the-loop systems, where device temperatures would not be controlled and might vary from -40 degree(s)C to 85 degree(s)C, has brought new challenges in laser reliability requirements. Also, lifetime assessment of lasers for the loop applications becomes increasingly more difficult as conventional constant power accelerated life test at 50 degree(s)C to 100 degree(s)C impose insufficient levels of stress. By studying comparatively the degradation behavior of different device structures, we have shown that the ridge waveguide laser structure may have potential for meeting the reliability requirement for such applications. Constant current stressing of the ridge waveguide laser at elevated temperatures of 150 degree(s)C to 200 degree(s)C indicated that the device degradation rate follows well-behaved log-normal distribution with standard deviation of 0.5. The activation energy determined from the experimental results was found to be about 0.88 eV. Projected laser MTTF at room temperature operation exceeds 107 hours, which is also in good agreement with results obtained from constant power life test at 50 degree(s), 70 degree(s), and 95 degree(s)C.
Degradation behaviors of GaAlAs/GaAs lasers have been studied and test results showed that the lasers degraded initially with a nearly constant rate of operating current increment followed by a rapid degradation mode. The time of onset of this latter mode differs for individual devices, but correlates well with the linear degradation rate at the start of lifetest. An analytic equation has been derived based on experimental data that covers a wide range of lifetimes, which could provide useful insight for the study of the possible mechanism responsible for the degradation behaviors, as well as for the development of a potential technique for reliability assessment of such lasers.
To accurately measure wavelengths of 1.3 and 1.5 micrometers single-mode sources, we developed a lambdameter that can be used in the near IR and the red regions of the spectrum. Wavelength accuracy and resolution are approximately equals 0.1 ppm (parts per million) at 0.633 micrometers . They were measured by comparing each of two adjacent modes of a HeNe laser, frequency- stabilized by a polarization technique, with a single mode from a second frequency-stabilized HeNe laser. We also verified the wavelength of the reference laser with an accuracy of 1 ppm by comparing it with the 1.52 micrometers HeNe laser line. The uncertainty in wavelength of the 1.52 micrometers HeNe laser is limited to the width of the Doppler gain curve, whose peak is known within 0.2 ppm. We describe our lambdameter and the performance of its reference laser as a wavelength transfer standard. Measurements on a commercially packaged 1.52 micrometers distributed-feedback (DBF) laser diode transmitter show that its wavelength fluctuates by at least 1 ppm during normal changes in room temperature.
A 780 nm self-pulsating compact disc (CD) laser has been incorporated into both 266 and 220 megabits/second (Mb/s) optical data links by IBM Rochester to interconnect computer systems. Fiber optic data links based on this short wavelength (SW) laser not only meet the cost and performance requirements of the data communications, but also overcome the major challenges of laser reliability and modal noise. To satisfy the stringent reliability requirements of data communication, standard CD lasers are screened through wafer selection and device burn-in procedures. Present lifetest results with more than 20,000 hrs of accelerated aging at 85 degree(s), 75 degree(s), and 65 degree(s)C indicate that the average failure rate of the screened CD laser can be less than 0.03% per khrs in a typical computer machine application. Additionally, because of the short coherence length, self-pulsating CD laser structures have solved the modal noise problem when this laser is used in conjunction with multimode optical fibers.
Water-cooled ion lasers have been commercially available for 25 years. Since the introduction of the metal-ceramic plasma tube technology 10 years ago, a considerable amount of research and development activity at Coherent has been devoted to improving the operating life and reliability of this kind of tube. The efficient generation of laser radiation imposes stringent requirements on the discharge parameters and, consequently, on the plasma tube itself. We have developed various methods to analyze the discharge environment, test the effectiveness of new materials and tube designs, and control the manufacturing process. The combined use of these methods allows the production of tubes with lifetimes that can exceed 10,000 hours in the visible wavelengths and 5,000 hours in the ultraviolet.
By measuring the effects of halogen concentration on the lifetime of KrF excimer laser, the impurities effects on the laser output performance are analyzed. The experimental results also show that the degration of halogen concentration is related to the laser resonator conditions.
Under laser inducement, we have observed steady state photoluminescence from poly(paraphenylene) and transient photoliininescence from PPP in nanosecond time regime for the first time. PPP samples studied were produced using the Kovacic method. The
experimental results indicate that the lininescence spectra are well-resolved. The peaks are rather sharp and located at 4340Å(100K), 4332Å(50K), 4318Å(8.5K) (transient state) and 4309Å, 4575Å (steady state). The luminescence spectra have been discussed by using the lattice
relaxation process. The lifetime of the luminescence of PPP was measured. The decay curve of PPP is found to have a double exponential form with a lifetime of 7.47 ns and 5.13 ns. The decay kinetics was interpreted by the interchain recombination of photoexcited polaron pairs. The decay kinetics of photoinduced absorption between a few nanoseconds and a few microseconds is mainly due to the interchain recombination of the photoexcited polaron pairs and exhibits the radiative luminescence after relaxation.
This paper discusses the reliability requirements and specific characteristics of solid state lasers in space-borne applications. For the purpose of discussion here, we refer to solid state lasers as those not employing active media in the gas or liquid state. Therefore we will cover both semiconductor laser diodes (principally GaAlAs/GaAs) and crystalline lasers (principally Nd:YAG). The paper is therefore divided into two major sections addressing each laser type.