Generic filters

NdYAG

808nm to 1064nm

(532nm along with KTP)

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NdYVO4

808nm to 1064nm

More efficient than NdYAG

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KTP

Convert 1064nm to 532nm

Economic Nonlinear Crystal

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CrYAG

Passive Qswitch

Sauterable Absorber

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What is Laser Crystal?

Laser crystals are optical crystals that are doped with laser-active ions and used as gain media for solid-state lasers. They can convert the energy supplied from the outside into highly parallel and monochromatic laser beams with spatial and temporal coherence. Laser crystals have different characteristics and properties depending on the type of dopant and host crystal. Some of the most common types of laser crystals are Nd:YAG, Yb:YAG, Ti:sapphire, Er:YAG, Nd:YLF, Nd:YVO4, etc. These laser crystals have different absorption and emission wavelengths, typical power ranges, and applications. The following table summarizes some of these parameters for some common laser crystals.

Laser crystal Absorption wavelength Emission wavelength Typical power range Application
Nd:YAG 808 nm 1064 nm 10 W – 10 kW Material processing, medical lasers, LIDAR
Yb:YAG 940 nm 1030 nm 10 W – 100 kW High power lasers, ultrafast lasers
Ti:sapphire 450 – 600 nm 650 – 1100 nm < 10 W Ultrafast lasers, tunable lasers
Er:YAG 940 – 980 nm 2940 nm < 100 W Medical lasers, dentistry
Nd:YLF 792 – 808 nm 1047 nm or 1053 nm < 10 W Ultrafast lasers, Q-switched lasers
Nd:YVO4 808 nm 1064 nm or 1342 nm < 100 W Diode-pumped lasers, frequency-doubled lasers
Common Laser Wavelength and Gain Medium

Major Properties of Laser Crystals

Laser crystals have several characteristics and properties that determine their performance and suitability for different laser applications. Some of these characteristics and properties are:

  • Doping: Laser crystals are doped with laser-active ions that provide the energy levels for optical transitions and stimulated emission. The type and concentration of dopant ions affect the absorption and emission wavelengths, the cross-sections, the quantum efficiency, the fluorescence lifetime, the saturation intensity, and the thermal loading of the laser crystal. For example, Nd:YAG is doped with neodymium ions that emit at 1064 nm with a high cross-section and a long lifetime, while Yb:YAG is doped with ytterbium ions that emit at 1030 nm with a lower cross-section but a higher quantum efficiency and a lower thermal loading.
  • Host crystal: Laser crystals are based on host crystals that provide the structural and optical properties of the gain medium. The host crystal affects the thermal conductivity, the refractive index, the birefringence, the mechanical strength, the chemical stability, and the crystal growth of the laser crystal. For example, YAG is a garnet host crystal that has a high thermal conductivity, a low refractive index, a cubic symmetry (no birefringence), a high mechanical strength, a good chemical stability, and a relatively easy crystal growth, while YLF is a fluoride host crystal that has a lower thermal conductivity, a higher refractive index, a tetragonal symmetry (birefringence), a lower mechanical strength, a poorer chemical stability, and a more difficult crystal growth.
  • Geometry: Laser crystals can have different geometries depending on the shape and size of the crystal. The geometry affects the mode structure, the beam quality, the output power, the efficiency, and the thermal management of the laser. For example, rod-shaped laser crystals are commonly used for high-power lasers with good beam quality and mode control, while thin-disk laser crystals are used for ultra-high-power lasers with high efficiency and thermal management.

These characteristics and properties of laser crystals influence the design and optimization of laser systems for various applications. By choosing the appropriate laser crystal for a specific application, one can achieve better performance and reliability of the laser system.

PROs and CONs of using Laser Crystal as Gain Medium

Pros of using laser crystals as gain medium:

  • Laser crystals have high transition cross sections, which means they have a high probability of absorption or stimulated emission. This leads to high optical gain and high energy conversion efficiency.
  • Laser crystals have high thermal conductivity, which means they can dissipate heat better and reduce thermal effects such as thermal lensing, thermal stress, and thermal expansion. This leads to better beam quality and stability.
  • Laser crystals have narrow absorption and emission bandwidths, which means they can produce monochromatic and coherent light beams with low noise and high spectral purity. This leads to better performance in applications that require high precision and resolution.

Cons of using laser crystals as gain medium:

  • Laser crystals have low repetition rates, which means they can only produce pulsed lasers with low average power. This limits their applications in high-power and continuous-wave lasers.
  • Laser crystals have complex operation, which means they require careful alignment, cooling, pumping, and mode control. This increases the cost and difficulty of laser systems based on laser crystals.
  • Laser crystals have limited tunability, which means they can only produce light at fixed wavelengths determined by the dopant ions and host crystals. This limits their applications in tunable lasers and broadband lasers.

Comparing of Different Types Lasers

Type of laser Gain medium Pump source Wavelength range Typical power Pros and cons
Gas laser Gas (e.g., CO2, He-Ne, Ar, Kr, Xe) Electrical discharge or optical pumping UV to IR 1 mW to 100 kW Pros: High beam quality, long coherence length, wide wavelength range. Cons: Large size, high power consumption, gas leakage, alignment issues.
Solid-state laser Solid (e.g., ruby, Nd:YAG, Ti:sapphire) Flash lamp or laser diode Visible to IR 1 mW to 10 MW Pros: High peak power, high energy conversion efficiency, compact size. Cons: Low repetition rate, high cooling requirement, thermal lensing.
Fiber laser Optical fiber doped with rare-earth ions (e.g., Yb, Er, Nd) Laser diode or pump laser Near-IR 1 mW to 100 kW Pros: High power conversion efficiency, high quantum efficiency, low thermal distortion, flexible delivery. Cons: Nonlinear effects, pump coupling loss, fiber damage.
Liquid laser (dye laser) Organic dye solution Pump laser or flash lamp Visible to near-IR 1 mW to 1 kW Pros: Tunable wavelength, high pulse energy, broad gain bandwidth. Cons: Low quantum efficiency, short dye lifetime, complex operation.
Semiconductor laser (laser diode) Semiconductor p-n junction (e.g., GaAs, InGaAs) Electrical current UV to IR 1 mW to 10 W Pros: Low cost, high power conversion efficiency, compact size, direct modulation. Cons: Low beam quality, temperature sensitivity, short coherence length.