Vertical Cavity Surface Emitting Laser - Coursework Example

Introduction to optical communications and its importance VCSEL – Vertical Cavity Surface Emitting Laser – is a semi-conductor micro laser diode that originates light in a cylindrical shaft of light directly from the exterior side of a manufactured wafer, and gives considerable return when contrasted to the edge-emitting lasers that are used in most of the fiber optic connections devices (Brian Milligan, 2004). In technological fields such as optical communications or others, there has been a considerable importance given to VCSEL (J.M. Ostermann, et al. 2005, pg. 511). Such surface emitting lasers have exceptional distinctiveness which edge-emitting semi-conductor lasers don’t have. For instance, these are distinguished by lesser entry current and little usage of power. With a Vertical Cavity Surface Emitting Laser, an encircling ‘ray spot’ can be attained readily (Brian Milligan, 2004). Also, assessment can be carried out whilst VCSELs are lying on a wafer, and beam springs can be set in multi-dimensional arrays. By means of this importance, demands particularly as ‘beam sources’ on the communication ground have been expected to develop. In this paper we shall briefly discuss ‘the basic requirements of optical sources used in communication systems’, ‘VCSELs’ advantages and disadvantages’, ‘the basic construction of VCSEL and the physics behind its performance’, ‘different types of VCSEL – its applications’, and the ‘synergy between VCSEL and the recently-invented photonic crystals’. The basic requirements of optical sources used in communication systems VCSELs are guaranteeing devices for usage in optical data links for corresponding broadcast and networking. The innate option for understanding 2D arrays, speedy modulation, and data formation make VCSELs the sources of selection for corresponding optical communication systems (J.M. Ostermann, et al. 2005, pg. 511). Because of higher wall-plug efficiency function at short driving currents, VCSELs can trim down thermal warming when making the usage of optical communications joined with speedy ICs in optical transverse modes. Optical transverse modules – both transmitter and receiver – have need of balanced packaging tools for edging CMOS chips and optical fibers (J.M. Ostermann, 2005, et al pg. 512). When a VCSEL is attached or connected to an ‘optical fiber’, it is attractive that laser beam are in a sole ‘transceiver modules’ or fundamental transceiver modules (J.M. Ostermann, et al 2005, pg. 514). This is due to a reason that lone transverse mode has little radiation angle and greater competence in pairing with an optical fiber or the resembling, as comparable to a multi-mode has. For that reason, there have been suggestions to hold back higher-order transceiver modules of laser beam emanated from a VCSEL (J.M. Ostermann, et al 2005, pg. 519). Advantages and Disadvantages Vertical Cavity Surface Emitting Lasers have various benefits like its building can be included in the configuration of multi-dimensional arrays; its lower entry currents allow higher-density arrays; its ‘surface-normal emanation’ is almost identical to the photo-detector geometry provide simple configuration as well as packaging; its encircling and less-deviated produced lights get rid of the requirement for corrective optics; its inactive vs. active alignment of fibers, amalgamated with higher fiber-connecting efficiency; its reasonably priced potential also a plus point of it, seeing that the devices are produced and experimented at the wafer level, and finally its lesser temperature-affected sensitivity judged against ‘edge-emitting laser diodes’ and its higher communication pace with less power use (Lasermate Corporation, Inc.).  On the other hand, the main drawback of VCSELs is that they have a tendency to have low production power (i.e., on the order of about hundreds of microwatts or less). Another weakness of regular VCSELs is their operational wavelengths are restricted to shorter wavelengths of approx. 850 nm to approx. 1300 nm (Patent Storm 2001). The basic construction of VCSEL and the physics behind its performance Vertical Cavity Surface Emitting Lasers can be constructed professionally on a three-inched diameter wafer (C. Lei et al. 1997, pg. 28). Even more significantly, the ability to create VCSELs by making use of standard micro-electronic manufacturing processes let the combining of VCSELs on-board with other constituents devoid of having pre-packaging. As an ‘allowing technology’, VCSELs let newer systems and creations to be produced cheaply (C. Lei et al. 1997, pg. 29). Little assemblage times and ‘easier schemes’ for automatic creation can be attained by making the usage of self-alignment methods, particularly for parallel communications with their higher number of ‘connected elements’. Higher-reflection mirrors are necessitated in VCSELs to balance the short axial measurement along the gained area. In general VCSELs ‘the upper and lower mirrors are doped as P-doped and N-doped mirrors, structuring a diode junction (C. Lei et al. 1997, pg. 30). In difficult constructions, the P-doped and N-doped perhaps hidden between the mirrors, needing a more intricate semi-conductor course to build electrical ‘relation’ to the active layer, but getting rid of electrical power failure in the DBR construction (C. Lei et al. 1997, pg. 33). Fig. 1: Designs and beam profiles of a) Edge-emitter, b) VCSEL (Online) Different types of VCSELs -applications of VCSELs There are various types of Vertical Cavity Surface Emitting Lases such as: first form is ‘Multiple active regional devices’ – devices that are allowed for differential quantum efficiency characteristics over 100 percent through carrier reprocessing. Second type of VCSEL is ‘VCSEL with tunnel junctions’ - using a tunnel junction, an electronically beneficial tool can be constructed that also may constructively influence other formational components (e.g., in the form of a Buried Tunnel Junction (BTJ)). Third one is a ‘Broadly adjustable VCSEL’ – a laser with micro-mechanically adjustable mirrors (Wikipedia). Fourth one is a ‘Wafer-bonded’ VCSEL – a grouping of semi-conductor resources that can be made-up by making use of different sorts of substrate wafers (Wikipedia). Fifth one is “Monolithically and optically pumped VCSELs” – these are two VCSELs over each other, one of them optically drives the other. Sixth VCSEL is with “longitudinally incorporated monitor diode” – a photodiode is incorporated under the back mirror of a VCSEL (Wikipedia). Seventh one is a VCSEL with “transversely incorporated monitor diode” – this one is with suitable etching of the VCSEL's wafer, a resonant photodiode can be manufactured that may measure the light intensity of a neighboring VCSEL. Eighth one is VCSEL with outer openings, known as ‘VECSELs or semiconductor disk lasers’. And the tenth and final one is ‘Vertical-cavity semiconductor optical amplifiers’, commonly known as VCSOAs (Wikipedia). The synergy between VCSEL and the recently-invented photonic crystals For VCSELs to be used in high-performance optical communication systems, generally higher power, steady, singled-module process is necessary – to discuss the synergy between VCSLEs and photonic crystals (K.H. Lee et al 2004, pg. 4136). By setting up several flaws into the Photonic Crystals, it was confirmed that in-phase consistent pairing inside a two-dimensional array could be executed, so opening the means for a storage laser resource. From this standpoint, photonic crystals with good visual excellence could be produced, yet on a ‘thick’ model having a distributed Bragg reflector (DBR) stack (K.H. Lee et al 2004, pg. 4143). It was viewed that because of the synergy in the photonic crystals production course, and resultant lessening of the balance of the photonic crystals networks, the duly-collapsed dipole like modes opening into two polarized modes, while the non-collapse modes confirmed no indication of opening. Conclusion From the above discussion, it is to be concluded that the huge production opening of VCSELs, contrasted to the majority of edge-emitting lasers, creates a minor deviation angle of the productivity ray, and causes high-pairing effectiveness with optical fibers. The higher reflective mirrors, evaluated to the majority of edge-emitting lasers, lessen the entry current of VCSELs, ensuing in lesser power use. Though, up to now, the lower entrance current also allows higher built-in modulation of bandwidths in Vertical Cavity Surface Emitting Laser. References: K.H. Lee, J.H. Baek, I.K. Hwang, Y.H. Lee, G.H. Lee, J.H. Ser, H.D. Kim, and H.E. Shin, “Square-lattice photonic-crystal (PCs) VCSELs”, Optics Express, 2004, 12, pp. 4136-4143. Donna Dickie, “Vertical Cavity Surface-Emitting Lasers”, 2006, 01245 491 499, Accessed March 11, 2008 http://www.lasercomponents.co.uk/wwwuk/news/vcsel.htm J.M. Ostermann, P. Debernardi, C. Jalics, A. Kroner, M.C. Riedl, and R. Michalzik, “Surface gratings for polarization control of single–and multi-mode oxide-confined vertical cavity surface emitting lasers”, Optics Communications, 2005, 246, pp. 511-519. C. Lei, L.A. Hodge, J.J. Dudley, M.R. Keever, B. Liang, J.R. Bhagat and A. Liao, “High-performance VCSELs for product applications,” in Proc. SPIE Conf. Vertical Cavity Surface-Emitting Lasers, vol. 3003, pp. 28-33, San Jose, California, 1997. See Wikipedia, Vertical-cavity surface-emitting laser, Accessed March 11, 2008, http://en.wikipedia.org/wiki/Vertical-cavity_surface-emitting_laser. Laser mate Corporation, “Vertical Cavity Surface-Emitting Lasers”, accessed Mar. 11, 2008 http://www.lasermate.com/vcsel.htm. PatentStorm, LLC., “Semiconductor laser having electro-static discharge protection”, February 6, 200,1Accessed March 12, 2008 http://www.patentstorm.us/patents/6185240-description.html Read More