The liquid crystal (LC) variable phase retarder (VPR)  is a transmissive device which permits to vary electrically the phase retardation of the element.  The device is ideal if robust and compact design is needed. This product   is interesting specially when working with polarized light (which is often the case when working with lasers). The Arcoptix phase retarder  causes only a few percent losses and its limited size permits to insert the element in the optical path of your system without to much troubles. The optical  retardation can be electrically tuned with the LC driver of ARCoptix but also with simple labor signal generator). Alternatively, in combination with polarizers the VPR can be used as optical valve (for a narrow wavelength range) or as polarization State controller (PSG). In summary :

• Simple and robust device        • Transmissive element        • Electrically Tunable	• for polarized light        • Optical valve (with extra polarizers)        • Polarization state controller
Scientific grade variable retarder 10mm aperture	Scientific grade variable phase retarder 20mm aperture

The liquid crystal variable phase retarder (VPR) is similar to a  waveplate (QWP or HWP). The major difference is that the VPR is electrically tuanble  and  is able to provide any phase shift from zero to several times the light wavelength by simply applying the right voltage (between (0 and 4 V). The VPR be used throughout the VIS and NIR region (400nm to 1800nm) without losses higher than 20%. Thanks to the use of thick substrates (scientific grade) and a special LC blends were are capable to offer robust equipment with minimal wavefront distortion and power absorption.

Contact ARCoptix for more information: info@arcoptix.com

Retarder type selection

The VPR product selection can be categorized as follow:

Driver (optional)

The VPR  can be driven with the Arcoptix LC (Liquid Crystal) driver which is a USB computer controlled electrical power supply optimized for driving the VPR. The bias that is applied on the VPR, which determines the phase retardation, is generated by the LC driver.  Since the driver has two independent outputs two VPR can be connected to the device. Also the user can computer control the device via labview or any other custom program the driver. 

Notice however that the VPR can also be driven with a standard labor function generator.

The LC driver has two independent outputs (Lemo connectors). They are controlled via a simple windows compatible software. The output has a variable square amplitude with polarity inversion and a frequency of 1.6 KHz. This guarantees  a homogenous variation of the LC layer inside the cell. An external trigger input can be provided on demand.

Specifications:

The table below summarizes the principal characteristics for the industrial grade and scientific grade cells:
 

Contact ARCoptix for more information: info@arcoptix.com

Working Principle

The Arcoptix variable phase retarders are manufactured with standard liquid crystal technology. As depicted in figure below, they are principally made of a LC layer sandwiched between two polished glass substrates coated with a transparent electrode (ITO) and a polyimide alignment layer. The two glass plates are precisely spaced apart with  glass fibers. The electric field that can be induced by applying a voltage on the transparent ITO electrodes (0-7V) modifies the alignment of the LC molecules and by the same way the apparent retardance of the cell. 

The Figure below shows three different cases for different applied votages: Figure (a) shows the alignment of the LC molecules when no voltage is applied. In this case the molecules are aligned along the glass plates and the retardance (along the optical axis) is maximal.

Figure (b) shows an intermediate state where we apply a small voltage of about 3V. In this case the molecules have an oblique orientation and the apparent retardation is somewhere in between the maximum retardation (several times the wavelength) and the minimum retardation (almost zero).

 Figure (c) shows the other extreme case where a “high” voltage (7V) is applied and the electric field forces the LC molecules to align perpendicularly to the glass plates (parallel to the electric field).

Price list

Devices	Price
VPR Industrial grade(22mm  without housing)	390 EUR
VPR Industrial grade(other aperture)	Ask
VPR Scientific grade(10mm .with housing)	790 EUR
VPR Scientific grade(20mm with housing)	1190 EUR
LC USB Driver(2 outputs)	590 EUR

For custom models please contact info@arcoptix.com for quotations

DOWNLOADS :

DOWNLOAD Description of the Variable phase retarder

	DOWNLOAD User Manual of the Variable phase retarder
	DOWNLOAD Description of LC USB Driver