Decades of work by researchers in the engineering field has led to a considerable amount of information regarding the stability of lasers, which has ultimately been pivotal in the development of reliable laser systems. Of the various lasers that exist, multi-stripe lasers have been shown to exhibit particularly complex spatiotemporal behavior. This unique characteristic of multi-stripe lasers is associated with forming self-organized and spontaneous dissipative structures in applied devices.
Understanding Laser Diodes
Although laser diodes share certain similarities with light-emitting diodes (LEDs) in terms of their power sources and wavelength range, laser diodes (LDs) are capable of dissipating a significantly greater fraction of power and heat compared to LEDs. Despite this, the high cost associated with LDs has often restricted their production. Some current applications of LDs can be found in material processing, projection displays and medical treatments as a result of their higher output light power.
Multi-Stripe Laser Diodes
In order to further increase the output power of LDs, users can choose either a single broad-area stripe emitter or multiple stripe emitters that have been monolithically integrated into a single laser chip. Multi-stripe lasers are comprised of multiple laser stripes that have been optically coupled through diffraction of evanescent fields and that transverse diffusion of charge carriers. An increased number of laser stripes, placed in close vicinity to each other, has been shown to improve the spatio-temporal intensity distribution of multi-stripe arrays. In fact, compared to single-stripe lasers, multi-stripe lasers exhibit a completely different dynamic activity, which has been confirmed through both theoretical and physical experimental procedures.
In order to focus multistripe LDs, the most conventional approach involves collimating the beam, compensating the different beam divergencies to become both parallel and perpendicular to the array, and ultimately focusing the beam to a circular spot.
How Reliable are Multi-Stripe Laser Diodes?
One method that has been accepted for analyzing the reliability of multi-stripe laser diodes, particularly GaAs based laser diodes, is the mean time between emitter failures (MTBEF) method. In this method, researchers can characterize and specify the reliability of multi-emitter pumps when these laser diodes are being used for ensemble applications. In a 2008 study that investigated GaAs multi-emitter modules, researchers found that the thermal acceleration effect caused multi-emitter modules to behave in a similar manner to single emitter modules.
Unique Applications of Multi-Stripe Lasers
Although many of the advancements behind intelligent autonomous robotic devices have been made over the past decade, a 2002 paper published by the International Society for Optical Engineering pioneered an innovative three-dimensional (3D) sensor system comprised of multi-striper lasers. Since robots require numerous sensor systems capable of recognizing and obtaining information regarding their surrounding environment, structured lighting is often a basic requirement for this purpose.
In their 2002 paper, a trinocular vision system composed of a flexible multi-stripe laser projector and two cameras was used. This sensor system utilized a multi-stripe laser projector that is capable of adjusting the width of the stripe lines. Furthermore, this projection system was also accompanied by a rotating polygon mirror that created laser slit beam sweeps on the area of interest, an assembly of LDs and a cylindrical lens to create the laser stripe.
Sources and Further Reading
- Weiss, O .(1994). Spatio-Temporal Complexity in Multi-Stripe and Broad-area Semiconductor Lasers. Chaos, Solitions & Fractals 4;8. 1597-1618.
- Brabec, T., Krausz, F., Wintner, E., Schmidt, A. J. (1991). Longitudinal pumping of lasers with multistripe laser diodes. Applied Optics 30(12); 1450-1451. DOI: 10.1364/AO.30.001450.
- Wolak. E., Kuppuswamy, K., Fidric, B., Park, S., Liu, D., Cutillas, S., et al. (2008). Reliability of ensembles multi-stripe laser diodes. SPIE. DOI: 10.1117/12.764348.
- Kim, M. Y., Cho, H. S., & Kim, J. H. (2002). A 3D sensor system using multi-stripe laser and stereo camera for environment recognition of mobile robots. SPIE. DOI: 10.1117/12.467350.