Generally, a solid-state laser is a laser that uses a solid-state laser gain medium which converts energy from an optical pump source to a coherent output laser beam. The optical pumping source may apply optical pump energy to the lasing medium so as to irradiate the lasing medium and effect a laser beam. The pump source can be one of many available energy-producing systems such as flash lamps or semiconductor laser diodes. The energy produced by the pump source is incident upon the laser medium and absorbed by the laser medium. Laser mediums often include dopant ions dispersed within the host glass or crystal. YAG (yttrium-aluminum-garnet) is a synthetic garnet of yttrium and aluminum oxide that is commonly used to generate laser beams in solid-state laser assemblies. The YAG crystal may be doped with neodymium (Nd), ytterbium (Yb), holmium (Ho), erbium (Er), thulium (Tm) ions, and may include, for example, ytterbium doped yttrium aluminum garnet (Yb:YAG), neodymium doped yttrium aluminum garnet (Nd:YAG) or erbium doped yttrium aluminum garnet or glass (Er:YAG, Er:crystal Er:glass). A solid-state laser usually use an efficient GaAlAs diode laser as a pump source whose emitting wavelength close 800 nm to pump a crystal doped with a laser active ion. Laser diodes have been recognized as providing an efficient pump source in solid-state laser systems. When employed as a pump source, the laser diode is used to generate light which overlaps the spectral band of the laser medium. Laser diodes emit a light beam with an elliptical shape. A laser diode array contains many individual laser diodes. Each diode emits its own laser beam from the emitting surface, which together form an elliptical light beam. Laser diode pump sources have high electrical-to-optical conversion efficiency, and the narrow-band spectral output of laser diodes can be chosen to closely match the absorption bands of solid-state laser materials. Diode-lasers are preferred as pump-light sources for solid-state lasers because they can be designed to emit at essentially any wavelength within a wavelength range determined by particular semiconductor materials used for their manufacture. The wavelength can be selected to match a preferred absorption band of a solid-state gain-medium being pumped. This provides that essentially the entire output of the diode-laser is effective in pumping the gain-medium. The laser diode is considered to be more efficient as a pump source than a flash lamp or an arc lamp since the light produced by the laser diode is more closely matched to the host laser medium.

A typical solid-state laser includes a laser cavity formed by two opposing mirrors, a solid state gain medium situated within the laser cavity, and an optical pump source for pumping the gain medium. A diode-pumped solid-state laser typically includes a rare earth doped solid-state gain medium pumped by optical radiation from a laser diode. The laser gain media are dopant ions incorporated in dilute concentrations in solid hosts. The slab-like form of the gain-medium is particularly suited for optical pumping by one or more diode-laser arrays. In one common form, the gain-medium is in the form of an elongated parallelepiped or rhomb. The laser gain medium can be optically excited to emit electromagnetic radiation by impinging a pumping beam on the laser gain medium. Solid-state lasers can be configured as amplifier stages or as laser resonators. The laser resonator includes at least two reflective surfaces located on either side of the laser medium. The laser resonator can be designed to continuously release a laser beam from the system. The resonator can also be designed such that when the energy oscillating through the laser medium reaches a predetermined level, it is released from the system as a high-power, short-duration laser beam. The emitted light produced from the solid-state laser system is generally coherent and exits the system in a predefined area. The pumplight energy in laser amplifiers and laser resonators may be derived from high power light emitting diode arrays. The pumplight energy raises the energy level of dopant ions within the lasing medium. In solid-state laser systems, atoms present in a crystalline or glass host material or medium absorb light produced by an external pump source and thereby achieve an excited state to generate light at a known wavelength. With the development of modern advanced technique, lasers at various wavelength ranges are in practical need. Solid state lasers have been designed to operate at various wavelengths, with the infrared bands proving to be particularly useful. Monolithic diode-pumped solid-state microlasers can output laser radiation in a wavelength range between 900 and 1400 nm, dependent upon the composition of the gain material and other factors. To provide these shorter wavelengths, diode-pumped solid-state lasers have been used in conjunction with a nonlinear optical material that performs second harmonic generation that effectively doubles a fundamental frequency.

Diode-pumped solid state (DPSS) lasers are generally considered the most practical source of laser radiation for applications requiring high efficiency and compact, low-weight, and rugged packaging. Diode-pumped solid state laser is compact in size, has a long useful life, capable of oscillating with a single longitudinal mode, and can perform a high frequency modulation. A DPSS laser produces laser light by pumping a resonator of a laser material with light from laser diodes, exciting atoms or molecules within the laser material. Diode pumped lasers involve semiconductor diodes which laser when excited by electrical current. The lasing portions of the semiconductors, typically PN junctions, are positioned near a laser medium, so that laser energy from the semiconductor diodes is directed into the medium, either directly or by lenses. When pumped by the laser energy from the diodes, the energy excitation levels build up within the atomic structure of the medium. In a diode-pumped solid-state laser, a laser diode supplies a pump beam into an optically resonant cavity in which solid-state gain material is disposed. Solid state lasant materials include crystalline or glassy host materials into which an active material, such as trivalent neodymium ions, is incorporated. The pump beam is at least partially absorbed by the gain material, causing lasant ions to make a transition to a higher energy level, which supplies the energy to support lasing operation. The DPSS laser is divided into an end pumping type and a side pumping type. End-pumped refers simply to those designs wherein the output of the laser diode pump source is coupled into the end of a laser rod. In an end pumping type of DPSS laser, when a pumping light radiated from a laser diode is incident upon a laser material after passing through a focusing lens, the DPSS laser forms the pumping light in beam mode at the laser material so as to output a lasing light through an output coupler. The side-pumped DPSS laser can be divided into sub-fields based on how the otherwise highly divergent diode radiation is coupled into the laser rod. Some side-pumped DPSS laser use optics such as a cylindrical lens or elliptical mirror, some use an optical waveguide such as a reflective cavity or fiber, and some use closely coupling the diodes to the rod.

Solid state laser has attracted much attention because of its high efficiency, long life, and its potential miniaturization. Solid-state semiconductor diode lasers have numerous applications in fields as varied as the automobile industry, medicine, scientific instrumentation, and telecommunications. Solid-state laser oscillating devices are capable of providing a high-power and stable laser beam, and thus are widely used in laser machining apparatuses for carrying out cutting, welding, etc. of metallic or nonmetallic materials. DPSS laser has high efficiency and a large output-power in a relatively small size compared to a regular laser. Accordingly, there is an increasing trend of applying the DPSS laser to an industrial technology such as marking or cutting. Solid-state lasers are used by the military as rangefinders to determine target distance. Single-frequency solid state lasers find many applications in coherent communications, laser radars, and as pump lasers for nonlinear optical frequency conversion, among other applications. In medical applications, solid state laser is used to produce a desired effect on various types of tissue. The laser energy interacts with the tissue through reflection, refraction or absorption. This interaction may be used to perform incision, excision, resection, vaporization, ablation, coagulation, hemostasis, and denaturization of various tissue.