Wide stripe single and dual wavelength mode semiconductor diode lasers

摘要

Wide stripe semiconductor lasers have a wide variety of applications in remote sensing, in materials processing applications such as drilling and welding, and as pumps for gas lasers. The emission spectra of simple cost-effective Fabry-Perot (F-P) lasers tends to be very broad, i.e. in the 5-10 nm range at very high power levels, making their use ineffective in some of the above mentioned applications. In order to overcome the problem faced by wide stripe diode lasers with respect to emission wavelength, external gratings such as volume Bragg gratings have been used. These external gratings not only significantly drive up the cost of such integrated systems but also have their drawbacks in that they are very sensitive to mechanical vibrations. This work has focused on the use of an internal grating, a distributed Bragg reflector (DBR) grating that was monolithically inserted into the gain section of a semiconductor laser. The result is a single wavelength mode semiconductor laser capable of delivering high power levels. These lasers were made to have an emission wavelength of around 980 nm. The concept of a wide stripe, single wavelength mode laser eventually led to the creation of a wide stripe, dual wavelength mode laser. These lasers, apart from delivering high power levels, were also made to oscillate on two specific predetermined wavelengths. The laser has two different DBR gratings that were placed next to each other within the gain guided cavity. The wavelengths of interest were determined by controlling the respective pitches of the DBR gratings in accordance with the Bragg condition. The difference frequency between both wavelength modes can be tuned to be in the terahertz (THz) range, leading to interesting THz frequency generation experiments and eventual applications.