What is Q switch?

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Q-switching can promptly switch between producing little or extremely high losses to the laser beam. This gadget is typically used in laser resonators to make it possible for energetic Q-switching of lasers, generating short, intense pulses with pulse lengths in the nanosecond variety. The Q switch can likewise be incorporated with the tilt tooth cavity to create pulses, but the optical switch’s particular needs are also different.

Acousto-optic Q switch

The most typical sort of Q switch is the acousto-optic modulator. As long as the acoustic wave is switched off, the transmission loss triggered by the crystal or glass sheet is extremely small, however when the sound wave is activated, the crystal or glass will create a solid Bragg representation, and also the loss produced by each pass is about 50%. Produces 75% loss. To generate acoustic waves, an electronic motorist needs RF power at 1W (or numerous watts in large aperture gadgets) and microwave frequency (RF) at 100MHz.

Many parameters require to be traded off in the gadget. For example, a tellurium dioxide product with a really high electro-optic coefficient needs extremely little acoustic power but has a modest damage limit. Crystalline quartz or merged silica can handle high light intensities yet call for higher acoustic power (RF). The needed acoustic power is also associated with the tool’s aperture: high-power lasers call for large aperture tools, which additionally need greater acoustic power.

The switching speed (or inflection bandwidth) is ultimately not restricted by the acousto-optic transducer but by the acoustic wave rate and the beam diameter.

To subdue reflections from optical surface areas, anti-reflection finishings are usually required. There are additionally Q switched active tools operating at Brewster’s Factor.


Tellurium dioxide (TeO2) crystal is an acousto-optic crystal with a top-quality variable and a neutrino discovery crystal with dual beta degeneration attributes. Considering that the all-natural abundance of 130Te is 33.8%, it does not require focus, and the expense is reduced, so TeO2 crystal becomes the front runner for the dual beta decay source.

Electro-optical Q-switching

Electro-optical Q switch is a type of Q-switch known as Pockels cells and electro-optical modulation cells.

Electro-optical Q-switching is a little more complicated in structure, needing a high-voltage (4000V) circuit plus a high-speed back-voltage circuit. The outcome power of electro-optical Q-switching is bigger, getting to tens of megawatts, and the pulse size can be pressed to 10ns. On high-power lasers, electro-optical Q-switching is often utilized. Generally, for high-performance lasers, electro-optical Q-switching is liked. On top of that, it is used in single-pulse lasers because of the flexible control of electro-optical Q-switching.

Q-switched integrated circuit lasers require high changing speeds, which need electro-optic modulators. Amongst them, the polarization state of light is altered by the acousto-optic result (Pockels impact). After that, the polarization state change is exchanged for loss inflection by using a polarizer. Compared to acousto-optic gadgets, it calls for higher voltage (need to get changing nanosecond rate) yet no RF signal.


LGS (La3Ga5SiO14) is a multifunctional crystal trigonal system and belongs to the same 32-point group as quartz. It has two independent electro-optic coefficients similar to those of BBO crystals. LGS crystals have excellent temperature stability, modest light damage limit, and mechanical stamina. Its half-wave voltage is relatively high but can be changed by the facet ratio. As a result, LGS can be used as a new electro-optical crystal, which can supplement the shortages of DKDP and LN crystals, and is appropriate for making Q-switches for medium-power pulsed lasers as well as various other electro-optical devices.

Passive Q switch

Passive switches are saturable absorbers caused by the laser itself. Amongst them, the loss presented by the Q switch itself is extremely tiny. Once enough power is saved in the gain medium, the laser gain will be more than the loss. The laser power starts to boost gradually, and once the absorber reaches saturation, the losses lower, the internet gain increases, and the laser power enhances quickly to form short pulses.


Cr4+: YAG crystals are generally used as passive Q-switches in passive Q-switched YAG lasers. Other products are offered, such as doped crystals and glasses, and semiconductor-saturable absorption mirrors are especially ideal for generating small pulse energies.

Co: Spinel

Co: Spinel crystal is a recently developed material with an exhaust wavelength of 1.2-1.6 μm, which is a reliable passive Q switch. It is widely used in eye-safe Er: glass lasers (1.54 µm) and is validated on lasers with wavelengths of 1.44 µm and 1.34 µm. Co: MgAl2O4 (Co: spinel) has a high absorption cross-section, which allows Q-switching of Er: glass lasers (flash and diode laser pumped) without intracavity concentrating, overlooking excited-state absorption, leading to high Q-switching comparison, That is, the proportion of the initial to saturable absorption signal is more than 10.

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