Solid-State and Semiconductor Lasers

M.S. Demokan, Mode-Locking in Solid State and Semiconductor-Lasers (Wiley, New York,... 

The direct modulation property of semiconductor injection lasers is one of their unique characteristics and this feature provides the potential for many scientific and commercial applications. Unlike other solid state and liquid lasers, modulating the injection current can directly control the optical output of the semiconductor laser. 

Semiconductor lasers have certainly advanced to the stage where in the near future they will replace the more common solid state and gas lasers that have been the workhorses in both the scientific and industrial arenas. Semiconductor lasers will be successfully modelocked and the resultant ultrashort ophcal pulses will be amph-fled to peak power levels approaching the kilowatt region. This will have a tremendous impact on the ultrafast laser community, by providing an inexpensive, efficient, and compact source for ultrafast nonlinear optical studies. In addition, real-time optical signal processing and optical computing will take one step closer to reality with this advancement. 

We have previously mentioned some laser systems with which a certain degree of tunability is possible (dyes and semiconductor lasers). However, during the past two decades a new class of tunable lasers has been developed tunable solid state lasers. They have definitively replaced dye lasers for some spectral regions, offering a higher... 

Lasers (Light Amplification by Stimulated Emission of Radiation) are devices which amplify light and produce beams of light which are very intense, directional, and pure in colour. They can be solid state, gas, semiconductor, or liquid. 

The primary difference among lasers is the lasing medium. Lasers can be broadly divided into four types solid-state lasers, gas lasers, dye lasers, and semiconductor lasers. 

Basov (1922-2001) and Aleksandr Prokhorov (1916-2002), two Russian physicists who independently discovered how to produce continuous output, something that Townes was unable to do. The three were cited for fundamental work in the field of quantum electronics, which has led to the construction of oscillators and amplifiers based on the maser-laser principle [29]. Since that time, many different types of lasers were developed—gas, solid-state, fiber, semiconductor, dye, etc.— and they have found use in hundreds of applications in virtually every field of endeavor such as the military, industry, law enforcement, medicine, entertainment, and basic research [29]. 

Several criteria have been used for classification the most common is the laser material. Accordingly, lasers can be grouped as solid-state, gas, dye and semiconductor lasers. ... 

Solid-state light emitters have become increasingly important in microelectronics and in our daily lives. We encounter light emitting diodes and semiconductor lasers... 

A diode, or semiconductor, laser operates in the near-infrared and into the visible region of the spectmm. Like the mby and Nd YAG lasers it is a solid state laser but the mechanism involved is quite different. 

Solid-State Lasers. Sohd-state lasers (37) use glassy or crystalline host materials containing some active species. The term soHd-state as used in connection with lasers does not imply semiconductors rather it appHes to soHd materials containing impurity ions. The impurity ions are typically ions of the transition metals, such as chromium, or ions of the rare-earth series, such as neodymium (see Lanthanides). Most often, the soHd material is in the form of a cylindrical rod with the ends poHshed flat and parallel, but a variety of other forms have been used, including slabs and cylindrical rods with the ends cut at Brewster s angle. 

One application of modem solid-state electronic devices is semiconductor materials that convert electrical energy into light. These light-emitting diodes (LEDs) are used for visual displays and solid-state lasers. Many indicator lights are LEDs, and diode lasers read compact discs in a CD player. The field of diode lasers is expanding particularly rapidly, driven by such applications as fiber optic telephone transmission. 

We can already deduce that, due to the characteristics of the active medium, compact and miniaturized devices are attainable for semiconductor lasers. This fact, together with the possibility of custom-designed systems, constitutes a real advantage from the viewpoint of integrated opto-electronic devices. In the field of spectroscopy, they are commonly used as pumping sources for other types of solid state lasers, as will be seen later. 

Most optical centers show luminescence decay times in the nanoseconds-milliseconds range. However, many other physical processes involved in optical spectroscopy are produced in the picoseconds-femtoseconds range, and mnch more complicated instrumentation becomes necessary. For instance, interband Inminescence in solids, which is of particular interest in semiconductors, can involve decay times in the range of picoseconds. Pulses generated from solid state lasers have already reached this femtosecond domain. 

N. Holonyak, Jr. and M. H. Lee, Photopumped III-V Semiconductor Lasers H. Kressel and J. K Butler, Heterojunction Laser Diodes A Van der Ziel, Space-Charge-Limited Solid-State Diodes P. J. Price, Monte Carlo Calculation of Electron Transport in Solids... 

---