Quartz Birefringent Filter Plates

The birefringent filter plate is a linear retarder made of a-cut (or 90^o cut with the optical axis in the plate face) crystalline quartz and used intracavity to selectively tune a desired wavelength and create reflection losses at other wavelengths. In use, it is placed at Brewster’s angle, and then rotated about the axis perpendicular to the surface to achieve a full wave retardation at the wavelength of interest. The selected wavelength contains only a p-polarization component, and thus experience no reflection loss. Other wavelengths undergo a different retardation, and have some amount of s-polarization, leading to reflection losses.

A birefringent filter used in a short-pulse laser cavity can be a single quartz plate. A birefringent filter for a narrow linewidth CW laser can contain a stack of 2–4 quartz plates, each plate being half the thickness of the previous one. The thickest plate sets the bandwidth and the thinnest the free spectral range (FSR).

Reference:

Birefringent filter for laser tuning: theory and design

The birefringent filter plates in this page have a thickness of multiples of T (T=0.5mm) with the diameter of 1" or 0.5". More quartz plates/blocks with various apertures, thicknesses and coatings are available under the general "Quartz Crystals".

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Part No.	Description	Application	Material	Wavelength	Bandwidth	Size	Aperture	Thickness	Length	Angle	Doping	Orientation	Displacement	Retardation	Delay	Coating	End cut	Holder	Price	Availability	Add to Cart

Basic Properties of Quartz Crystal:

Transparency Range: 200 - 2300 nm			Transmission Curve
Crystal Symmetry: Hexagonal, P3121
Lattice Constants: a=b=4.9133A, c=5.4053A
Density: 2.65 g/cm³
Thermo-Optic Coefficients: dno/dT= -0.52 x 10^-6 /^oC @ 530 nm dne/dT= -0.63 x 10^-6/^oC @ 530 nm
Damage Threshold ( 10ns, 10Hz) ~ 1GW/cm² at 1064 nm ~ 500 MW/cm² at 532 nm
Optical Homogeneity: Δn < 10^-6/cm
Mohs Hardness: 7
Thermal Expansion Coefficients:			α_a = 14 x 10^-6/K α_c = 7.6 x 10^-6/K
Linear Absorption Coefficients: α<0.01cm^-1 from 300 to 2300 nm
Sellmeier Equations: (λ in µm) : n_o²=2.3573-0.01170λ²+0.01054/λ²+1.3414x10^-4/λ⁴-4.4537x10^-7/λ⁶+5.9236x10^-8/λ⁸ n_e²=2.3849-0.01259λ²+0.01079/λ²+1.6518x10^-4/λ⁴-1.9474x10^-6/λ⁶+9.3648x10^-8/λ⁸
Wavelength(nm)	n_o	n_e	Birefringence (Δn=ne-no)	Walk-off Angle at 45°
1064	1.5341	1.5428	0.00872	-0.325°
800	1.5384	1.5473	0.00891	-0.331°
632.8	1.5427	1.5517	0.00906	-0.336°
532	1.5469	1.5561	0.00920	-0.340°
400	1.5577	1.5673	0.00957	-0.351°
355	1.5646	1.5744	0.00982	-0.358°
266	1.5916	1.6024	0.01077	-0.386°

Specifications:

Cut Orientation:	a-cut +/-5 arc min with the optical axis (c-axis) in the plane surface
Diameter Tolerance:	+0, -0.25 mm
Thickness Tolerance:	+/-0.05 mm for T=<5mm, +/-0.1 mm for T>5mm
Surface Quality:	10/5 Scratch and Dig
Parallelism:	< 3 arc sec
Perpendicularity:	<10 arc min
Transmission Wavefront Distortion:	<λ/8 @632.8 nm
AR-coating:	R<0.2% at the central wavelength is available upon request

Cut orientation (a-cut):

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