A Passive Q-switch is a device that can accomplish Q-switching by making use of the fact that the transmittance of optical material depends on the laser strength at a certain wavelength. The laser freeze linker mainly creates saturated absorbing crystals in passive Q-switch crystals. The absorption coefficient of saturated absorption crystal lowers with the boost of event light strength. When the saturation value is reached, the loss (Q worth) in the laser cavity is modulated, and also the pulse is released.

Some passive Q-switch crystals are listed here:

Co: Spinel

Co: Spinel crystal, called cobalt spinel, is a newly established product. Its discharging wavelength range is 1.2-1.6 μm, which has been verified to be a really efficient passive Q-switch switch. It is widely made use of in the eye-safe Er: glass laser (1.54 µm) as well as has actually been confirmed in lasers with wavelengths of 1.44 µm and also 1.34 µm. Co: Mgal2o4( Co: spinel) has a high absorption cross-section, allowing Q switching of Er: glass lasers (flash and also diode laser pumps) without cavity concentrating. The negligible fired-up state absorption causes a high contrast proportion of the Q switch. That is, the ratio of the first to saturated soaked-up signal is more than 10.

The major qualities of Co: Spinel crystal:

  • 1.3 to 1.6 mu m within the extent of the reduced optical loss
  • High damage threshold

Main applications of Co: Spinel crystals:

  • Passive q-switched @ 1.54 microns


V: YAG crystal, the Chinese name vanadium-doped yttrium aluminum garnet, is a fairly new crystalline material. Ideal for 1.06 ~ 1.44 μm laser exhaust, particularly for 1.3 μm Nd laser. The absorption top cross-section of the thrilling state is not noticeable near the absorption peak of 1300 nm. This material has outstanding optical, mechanical, and thermal properties. It can be created by the Czochralski approach. V: YAG crystals can be used in Nd: YAG, Nd: YAP, Nd: KGW, Nd: YVO 4, and also various other energetic media to acquire the passive Q-switched laser with the small framework and also outstanding efficiency.

Main qualities:

  • High-ground state absorption
  • Not obvious ecstatic state absorption
  • Q switch high contrast
  • Excellent optical homes, mechanical properties, and also thermal buildings
  • Ultraviolet immune high damages threshold

Main application:

  • Utilized in laser rangefinder, laser radar, and the passive tuning Q laser LIBS system


Cr4+: YAG crystal, Chinese name chromium doped yttrium aluminum garnet, is a perfect product for Q switching of laser (Nd: YAG as well as other doping Nd or Yb) with wavelengths from 0.8 to 1,2 μm. A notable attribute of Cr4+: YAG is its high damage limit of 500-1000 MW/cm2. Its absorption band prolongs from 800 nm to 1200 nm as well as reaches its top at regarding 1060nm, with a very large cross-sectional area of absorption peak.


  • 500-1000 MW/cm2 high damages threshold
  • extremely steady chemical as well as reliability
  • good thermal conductivity, lengthy lifespan
  • compact passive Q switch
  • simple to run

Main application:

  • Used for laser range finder, LIDAR, and also LIBS passive adjusting Q laser system
  • Need a short pulse laser system.


In 1991, it was uncovered that Cr: YSO( pure tetravalent chromium collection) solid-state saturable absorbing could be utilized for laser applications.

In 1993, Chen et al. used Cr: YSO solid-state saturable absorber to properly act on a 694.5 nm ruby laser,

The crystal’s wide-band absorption range (coming to a head at 390 nm, 595 nm, 695 nm, as well as 750 nm) expands from the noticeable area to the near-infrared region, making it an excellent switch for many lasers.


Cr4+: GSGG can be made use of as a passive Q-switch in the 1.06 μm band. Compared to the typical Cr4+: YAG passive Q-switched crystal, Cr4+: GSGG crystal has the following benefits:

The noticeable component is transparent (calibration) and is more advantageous to the laser light path,

In 1.06 mu m band have a better absorption coefficient. At the same time, it additionally has a strong ability for anti-irradiation.


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