| Light
Source |
Single
wavelength: He/Ne laser, laser diode; Spectroscopic:
quartz halogen lamp (> 400 nm) or Hg/Xe
lamp (> 200 nm) |
| Polarisers |
UV-grade
Polaroid (depending on required wavelength
range) |
| Birefringence
Modulator |
3
component high stability design, susprasil
optical element with transmission to 200 nm,
50 kHz modulation frequency |
| Detector |
End-on
photomultiplier or UV enhanced high sensitivity
silicon photodiode |
| Beam
Size |
1
mm or larger depending upon light source.
Focussing optics available for 10 µm
beam size with laser source |
| Table |
Ultra
high rigidity table with incident and reflection
arms in vertical plane. Arms separately driven
by stepping motors with angular resolution
of 1/20 degrees.Table allows rotation of arms
through 360°. Closest angle between arms
20°. 140 mm free diameter in center of
table. XYZ adjustable sample mount |
| Electronics |
Dual
analog lock-in amplifier at 50 kHz and 100
kHz frequencies provides simultaneous reading
of
Re(r) and Im(r) |
| Sensitivity |
Im(r),
Re(r) < 10-5
at 1 s response time (reflection from glass).
Sensitivity is reduced at shorter time constants
(variation is roughly proportional to t-1/2) |
| Speed |
Fastest
response time is 1 ms |
| Computer
Control |
Software
implemented as extension to the IgorPro data
analysis package by WaveMetrics running on
Windows NT/2000. A Microcontroller acts as hardware
interface and data logger for true real-time
operation. The control software allows simultaneous
instrument control and on-line data analysis.
A notebook computer can be used as the host
without additional hardware. Contact us for
information on support of Macintosh PowerPC
systems |
| Data
Analysis |
Simulations
of ellipticity are provided for layers on
substrates, as a function of angle of incidence,
layer thickness, substrate and film optical
anisotropy. |
