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United photonics Technology
Diffusion Bonded Crystal
Bonding (Diffusion bonded) crystals consist of one laser crystal and one or two undoped material. They are combined by optical contact method and further bonded under high temperature. Diffusion Bonded Crystal helps to decrease thermal lens effect considerably.

UPT can supply various standard assembly types as follows:

Material

Doping concentration(atm) or Optical Density(cm-1)

Aperture (mm)

Length of laser crystal(mm)

YVO4+ Nd:YVO4 + YVO4

0.1%-3%

1x1-20x20

0.15-30

�¦2-15

YAG+Nd:YAG+ YAG

0.1%-2.5%

1x1-20x20

0.125-200

�¦2-15

YAG+Nd:YAG+Cr4+:YAG

0.1%-2.5% / 0.6~7

1Ã??1-20Ã??20

0.125-200

�¦2-15

YAG+Nd:Ce:YAG+ Cr4+:YAG

0.6~7

1Ã??1-20Ã??20

0.125-200

Fabry Parot Etalon is a high-resolution interference spectrometer with wide applications, which include high-resolution spectroscopy, the study of spectral lines with very close wavelengths, such as the isotope spectrum of elements, the hyperfine structure of the spectrum, the small frequency shift in light scattering, the Doppler shift of spectral lines caused by atomic movement, and the internal structure shape of spectral lines.

It can also serve as a high demanding optical filter and a precision wavelength meter. In the laser system, it is often used to narrow the spectral line in the cavity or make the laser system operate in a single mode. It can be used as a bandwidth control and tuning device in broadband picosecond lasers to detect and analyze the spectral components in the laser (longitudinal mode, transverse mode).

Use of etalon and selection of substrate materials

Etalons, when used in transmission mode, have a series of transmittance peaks with periodic frequency spacing and are typically used in telecom for wavelength locking. Etalons are characterized by their Free Spectral Range (FSR) the frequency spacing between peaks and their Finesse which essentially governs the shape of the transmission peaks.
Etalon filters typically consist of a single spacer layer with two reflector stacks on either side.

For FSR values below 1000 GHz, the spacer is usually fabricated from a substrate material (rather than grown in thin film deposition). To achieve etalon quality polishing the parallelism of the substrate needs to be better than 1-5 arc-seconds.

Different substrate materials are chosen depending on the application fused silica is used when the etalon FSR and peak variation with temperature is to be minimized while Si is used when a high FSR temperature coefficient is required for thermal tuning.

Photonchina fabricates custom high quality fused silica and Si etalons at competitive prices with FSR values in the range of 12.5 GHz to 500 GHz.

Types of Etalon
The optical etalon can be a single-piece structure with parallel reflective surfaces, the solid-state etalon made of fused silica material, or an air-gap structure using a Fabry-Perot cavity double-reflective mirror, i.e., the air-gap etalon.
1. Solid Etalon:
Photonchina Specifications:
Material: H-K9L/BK7, Quartz Glass

Terbium Gallium Garnet(TGG) as a magneto-optical crystal, is an optimum material for Faraday devices (Rotator and Isolator) in the range from 400nm-1100nm, excluding 470-500nm.The Faraday rotator consists of a TGG rod contained inside a special designed magnet. The rotation sense of the polarization of a light beam passing through the rotator only depends on the direction of the magnetic field and not on the direction of propagation of the light beam. The optical isolator is a Faraday rotator set between two suitably aligned polarizers which allows a light beam to pass through in one direction only.Photonchina TGG has a combination of excellent properties such as large Verdet constant, low light loss, high thermal conductance and high light damage threshold which makes it a unique material for Faraday devices particularly suitable for YAG lasers and Ti: sapphire tunable lasers, ring lasers and seed injected lasers.

What are diffusion bonded crystals?

Diffusion bonded crystals are composed of a laser crystal and other undoped materials. They are optically contacted first and then bonded further under high temperature. Diffusion bonded crystals are able to significantly mitigate thermal lensing effect of laser crystals, thus providing integral components for compact lasers. Photonchina has been supplying standard assembly and special customized bonding crystals for customers in various applications. These diffusion bonded composite crystals have different wedge structures, Brewster angles, etc. It is mainly used to effectively reduce the thermal effect of solid-state high-power lasers.

Diffusion bonding production in Photonchina:

1)Optical contact between the crystals to be bonded.
2)Increase the temperature of crystals to 2/3 of the melting point in a gradual way and exert pressure to combine the two parts together.
3) Hold on the bonded crystals for a certain period at this high temperature, diffusion effect takes place.
4)Cooling slowly the crystals (24 hours) down to room temperature.

Products range of Photonchina:
1) YVO4+ Nd:YVO4 + YVO4; GdVO4+ Nd:GdVO4 + GdVO4;
2) YAG+Nd:YAG+ Cr4+:YAG; YAG+Nd:Ce:YAG+Cr4+:YAG; YAG+Yb:YAG+Cr4+:YAG
3) YLF+Nd:YLF+ YLF; YLF+Pr:YLF+ YLF
4) YAG+Ho:YAG+YAG; YAG+Tm:YAG+:YAG; YAG+Nd:YAG+ YAG
5) Tisapphire+Sapphire
6) KTP+ KTP
7ï¼?BBO Diffusion Bonded

Applications:
1)Industrial laser.
2)Biomedical laser, medical laser, beauty laser;
3)Semiconductor pump.
4)High-power operations.
5)Laser ranger finder.
6)High power laser system.
7)Laser Lidar.