Laser Crystals and Components

Laser Materials

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Teledyne FLIR Laser Crystals and Components offers high quality Yttrium Orthoaluminate, also referred to as yttrium aluminum perovskite (YAP), doped with Tm, Nd, Pr, Er and Cr.

YAP´s hardness and thermal conductivity are similar to YAG, but exhibits a highly anisotropic thermal expansion coefficient and is birefringent. YAP is an orthorhombic negative biaxial crystal belonging to the D162h (Pnma) space group. Emission wavelengths are polarized, and emission and absorption cross sections are dependent upon the crystallographic orientation. Teledyne FLIR Laser Crystals and Components (along with references [1] and [3] below), use the Pnma space group convention for defining the crystallographic a, b, and c-axis lattice constants. Others (including reference [2]) use the Pbnm convention. In the table below, we related the two conventions thru their common lattice constants.

The Basic Composition of AOTF

1.Acoustooptic medium: usually transparent crystalline materials, such as Quartz, rubidium aluminum phosphate (RbTiOPO4), Silicon, etc.

2.Transducers: Piezoelectric crystals (such as barium titanate) convert electrical signals into ultrasonic waves.

3.Drive electronics: Provides an adjustable RF signal to drive the transducer.

Working Principle

1.Sound waves travel through a medium:

When the transducer receives the RF signal from the driving electronics, it generates ultrasonic waves.

The ultrasonic wave propagates in the acousto-optic medium, which causes the refractive index of the medium to change periodically, forming a structure similar to the grating.

2.Diffraction of light:

When the incident light passes through the acousto-optic medium, it is affected by the periodic refractive index change caused by the sound wave.

This change will cause the incident light to diffract, divided into multiple diffraction orders (such as 0, 1, etc.).

3.Wavelength selection:

By changing the frequency of the RF signal, the wavelength and frequency of the sound wave will also change, thus changing the period of the grating formed.

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Because the diffraction Angle and diffraction efficiency of light are related to the grating period, different wavelengths of light diffract at different angles.

By precisely controlling the frequency of the RF signal, it is possible to selectively diffract and transmit specific wavelengths of light.

4.Beam separation:

The diffracted light of a particular wavelength can be separated by an appropriate optical element (such as a prism or lens), and the undiffracted light continues to travel along its original path.

AOTF Calculation Formula:

The acousto-optical interaction can be described in terms of the Bragg diffraction condition. By adjusting the frequency of the RF signal, Λ can be altered, thereby enabling selective tuning of λ.

• Λ represents the wavelength of the sound wave

• θ denotes the angle between incident light and diffracted light

• m signifies the diffraction order

• λ refers to the wavelength of light 

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