Solid State Lasers Information
Solid state lasers use a transparent substance (crystalline or glass) as the active medium, doped to provide the energy states necessary for lasing. The pumping mechanism is the radiation from a powerful light source, such as a flash lamp. Laser material choices for solid state lasers include Nd: Yag, ND: YVO 4, Nd: YLF, Alexandrite, and Ti: sapphire. Solid-state lasers using yttrium aluminum garnet as the matrix material, doped with neodymium (Nd:YAG) can have wavelength outputs of 1.064 µm, 532 nm, 473 nm, 355 nm, or 266 nm. Solid-state lasers using yttrium orthvanadate crystal as the matrix material, doped with neodymium (Nd:YVO4) can have wavelength outputs of 1.064 µm or 532 nm. Solid-state lasers using LiYF4 crystal as the matrix material, doped with neodymium (Nd:YLF) can have wavelength outputs of 1.313 µm, 1.053 µm, 527 nm, 523 nm, 351 nm, or 263 nm. Alexandrite, the common name for chromium-doped chrysoberyl (Cr3+ : BeAl2O4), is a solid-state crystal. It is a four-level, low-gain, and broadly tunable laser (nominal range 700-820 nm) using the energy levels of trivalent chromium in the crystalline host. A solid-state laser using sapphire as the matrix material, doped with Ti can have wavelength outputs of 700 nm-1.020 µm.
The power supply for solid state lasers can be internal or external. Output choices are continuous wave and pulsed. A Q-switchable solid state laser has a device used to rapidly change the Q of an optical resonator. It is used in the optical resonator of a laser to prevent lasing action until a high level of inversion (optical gain and energy storage) is achieved in the lasing medium. When the switch rapidly increases the Q of the cavity, a giant pulse is generated.
Important laser performance specifications to consider when searching for solid state lasers include wavelength range, beam size and beam divergence. Wavelength range refers to the wavelength(s) the laser produces. The beam size refers to the largest dimension of the beam when exiting the laser. Beam divergence refers to the change in beam size as a function of distance from the laser. Important laser geometry specifications to consider include length, width, height, and laser weight. Common continuous wave laser specifications include average power, longitudinal mode spacing, and noise RMS. Average Power is the power (in watts) of a continuous wave laser. Longitudinal mode spacing is the frequency spacing between the longitudinal modes, often called the free spectral range of the laser resonant cavity. Noise, RMS is the root mean square change in amplitude due to noise. Pulsed laser specs to consider include pulse energy pulse length, and repetition rate. The pulse energy is the energy per pulse of the laser. The pulse length is the length in time of a pulse. The repetition rate is the number of pulses per second.