The basic operating principles of gain guided tapered lasers are studied in detail by means of numerical simulations. The carrier induced lensing effect caused by spatial hole burning is described as ...the main mechanism limiting the device performance. The influence of the following design parameters in the maximum output power and beam brightness is analyzed: refractive index step of the ridge waveguide section, angle and length of the tapered section, and the use of beam spoilers. The results provide design guidelines for improving the device performance.
Q-switching is a well-known technique which can be applied to produce high peak-power and short duration optical pulses from different types of laser sources. It consists in modulating the losses of ...the laser cavity, either actively or passively, in such a way that the power accumulated during the off time, when the losses are high, is released during a short time interval when the losses are low. Q-switching in semiconductor lasers has been previously studied and simulated using a rate-equation model (REM) 1, but as far as we know it has never been applied to optical frequency comb (OFC) generation.
Dual-comb interferometry (DCI) is a measurement technique that has been proven very useful for many applications such as spectroscopy, ranging, or fiber sensing. It relies on the interference in a ...photodetector of two mutually coherent optical frequency combs (OFCs) with slightly different repetition frequencies. The result is a down-converted RF comb whose teeth are evenly spaced by the difference of the repetition rates of the two OFCs. DCI enables a high-resolution measurement of a device under test by a single and fast acquisition, using a setup with no moving parts and low-bandwidth electronics. The resolution of the technique is limited by the comb spacing. For this reason, many efforts have been made to reduce the frequency separation of the comb lines 1 which is usually larger than tens of MHz.
We study the influence of a patterned contact design on the beam properties of high-brightness tapered lasers. A simple approach to simulate patterned injection has been developed and introduced into ...a quasi-three-dimensional tapered laser model. The method is applied to tapered lasers, whose performance is limited by two different mechanisms: self-focusing and poor modal filtering. The results show an improvement in beam quality in comparison to standard devices.
Utilizing small-signal direct modulation and relative intensity noise measurements, the authors investigate changes in the modulation response, the differential gain delta g/ delta n, the nonlinear ...gain coefficient in , and the damping factor K, which result from three structural modifications to GaAs-based multiple quantum well lasers: the addition of strain in the quantum wells; and increase in the number of quantum wells; and the addition of p-doping in the quantum wells. These modifications are assessed in terms of their potential for reducing the drive current required to achieve a given modulation bandwidth, for increasing the maximum intrinsic modulation bandwidth of the laser, and for improving the prospects for monolithic layer/transistor integration. It has been possible to simultaneously increase delta g/ delta n and decrease K, yielding very efficient high-speed modulation (20 GHz at a DC bias current of 50 mA) and the first semiconductor lasers to achieve a direct modulation bandwidth of 30 GHz under DC bias.< >
Lymphangioma circumscriptum of the vulva Esquivias Gómez, J I; Miranda-Romero, A; Cuadrado Vallés, C ...
Cutis (New York, N.Y.),
03/2001, Volume:
67, Issue:
3
Journal Article
Lymphangioma circumscriptum is a benign disease of the lymph ducts and an unusual pathologic process that rarely affects the vulva. The etiology of this lesion is not clear, but obstruction of the ...lymph vessels has been suggested as a possible cause in some cases. We report the case of a 44-year-old woman with lesions similar to lymphangioma circumscriptum of the vulva and chronic idiopathic lymphedema of the lower right limb. Because there was no obvious cause, we propose that the lymphangioma was caused by the lymphedema.
We present an educational software addressed to the students of optical communication courses, for a simple visualization of the basic dynamic processes of semiconductor lasers. The graphic interface ...allows the user to choose the laser and the modulation parameters and it plots the laser power output and instantaneous frequency versus time. Additionally, the optical frequency variations are numerically shifted into the audible frequency range in order to produce a sound wave from the computer loudspeakers. Using the proposed software, the student can simultaneously see and hear how the laser intensity and frequency change, depending on the modulation and device parameters.
