Liquid Crystal on Silicon - Spatial Light Modulator

Priciple of Modulation
The LCOS chip has a parallel-aligned nematic liquid crystal layer to modulate light. It only changes the phase of light without any change of intensity and rotation of polarization state. Phase modulation is changed according to the alignment of the LC. The LC alignment is controlled, pixel by pixel, using a CMOS backplane and a DVI signal via a PC.

X10468 Series

There are 7 standard types of the X10468 series available. The X10468-01/-07/-08 have no dielectric mirror but have higher diffraction efficiency and covers the wide wavelength range of the readout light spectrum. The X10468-02/-03/-04/-05 have a dielectric mirror for a specified wavelength range. Figure 1 shows the spectral response for these types. An undesired interference noise will be appeared at the wavelength range from 700 nm to 900 nm for the X10468-07 and from 1150 nm to 1400nm for the X10468-08 owing to the reflection loss. The ultra violet light will cause a damage at the wavelength range less than 400 nm for the X10468-05. Please consult us the details. Hamamatsu produces OEM devices that meet your requirements in the wavelength range from 355 nm to 1550 nm. We are able to design and optimize device elements according to light wavelength used in your application.

Figure 1 : Spectral response of the X10468 series

Operating Characteristics
Light Utilization Efficiency
The X10468 series have high light utilization efficiency, which is defined a ratio of the 0th order diffraction light intensity to the input light intensity. The high light utilization efficiency mainly depends on reflectivity, and the amount of diffraction loss caused by the pixel structure. We adopted advanced CMOS technology to make diffraction loss smaller. As a result, the diffraction loss is less than 5 %. The X10468-2/-03/-04/-05 have a dielectric mirror which has high reflectivity. Therefore, these types have very high light utilization efficiency about 90 %. The X10468-01/-07/-08 have relatively low light utilization efficiency about 72 % compared to the ones with dielectric mirror but have wide spectral response characteristic.
Phase Modulation
	Figure 2 : Phase Modulation
The X10468 series can achieve phase modulation of more than 2 radians over the 400-1100 nm readout wavelength range. The X10468 series comes pre-calibrated from the factory for a specified wavelength range to have more than 2  radians of phase modulation and its linear characteristics. Figure 2 shows typical phase modulation characteristics. A phase shift of 2   radians or more and a linear phase response are achieved. The phase modulation curves for 95 % pixels lies within +/- 2 .

Diffraction Efficiency
The X10468 series is a pure phase SLM with high precision phase control; therefore, it has high diffraction efficiency close to the theoretical values. Figure 3 shows images of diffracted spots, when a multi-level phase grating is formed in the X10468 and Figure 4 shows typical diffraction efficiency characteristics. Here, diffraction efficiency is defined I1/I0, I1 is intensity of the 1st order diffraction spot, I0 is the intensity of the 0th order light when no pattern is displayed.
Figure 3 : Diffracted spots images		Figure 4 : Diffraction efficiency
(a) No pattern
(b) 2-level grating (25 lp/mm)
(c) 4-level grating (12.5 lp/mm)

Output Images
The X10468 series has high precision phase control and high diffraction efficiency, and is very suitable for holographic applications. Figure 5 (a) is a interferometer picture of output wavefront with a flatness calibration. The image in Figure 5(b) was reconstructed as the 1st diffraction order of the kinoform through the Fourier transform optics. Figure 5(c) shows a clear Laguerre Gaussian (LG) beam of (0, 1) order.
(a) Interferogram of output wavefront with calibration Area: 800 x 600 pixels RMS: 0.05 (=633 nm)	(b) Reconstructed image of CGH	(c) LG beam

Specifications

Parameter		X10468 series							Unit
		-01	-02	-03	-04	-05	-07	-08
Input signal		Digital Video Interface ( DVI )							---
DVI signal format		SVGA ( 800 × 600 pixels )							---
DVI frame rate		60							Hz
Number of input levels		256 ( 8 bits)							levels
Effective area		16   12							mm
Maximum spatial resolution		25							lp/mm
Fill factor		95							%
Response time *1	Rise	10 (633 nm)	25 (785 nm)	30 (1064 nm)	15 (532 nm)	15 ( 405nm)	15 ( 1064nm)	30 ( 1550nm)	ms
	Fall	35 (633 nm)	65 (785 nm)	80 (1064 nm)	30 (532 nm)	30 ( 405nm)	70 ( 1064nm)	140 ( 1550nm)	ms
Readout light wavelength		400 - 700	800±50	1050±50	510±50	410±10	620 - 1100	1000 - 1550	nm
Input voltage (AC)		100 to 230 ( 50 Hz / 60 Hz )							V
Power consumption		50							VA
Weight (Head)		Approx. 450							g
Weight (Controller including cables)		Approx. 4100							g

*1 Time required to change from 10 % to 90 % for 2 modulation.

Dimensional Outlines  (Unit: mm)