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Electro-optic modulators

Low Voltage Electro-Optic Light Modulators
Type: EM 200A, EM 200K & EM 200L

EM 200A
This is a low voltage ADP transverse electro-optic modulator designed to operate at all wavelengths in the visible and is entirely free from piezo-electric resonances. This modulator has a high degree of temperature stability, but where long term d.c. amplitude is required it should be operated in a constant temperature environment. The modulation frequency is not limited by the device characteristics other than by its electrical capacitance and therefore depends on the drive circuit used. Wide band ar-coatings are used on all components.
 

EM200 low voltage elctro-optic modulator

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EM 200K
This is a low voltage transverse KD*P electro-optic modulator designed to give maximum thermal stability beyond that obtained by the ADP type. Its transmission range is extended into the infra-red and its extinction ratio is also better than that obtained from its ADP counterpart. It does however display piezo-electric characteristics.
 
EM 200L
This is a low voltage transverse electro-optic modulator using high damage threshold lithium niobate. It has similar characteristics to the EM 200K with an optical range extended further into the infra-red.

Low voltage electro-optic light modulators specifications

Model No. EM 200A EM 200K EM 200L
Crystal Type ADP KD*P LiNb03
Aperture 2.2mm 2.2mm 2.2mm
Crystal Length 4 x 20mm 2 x 40mm 2 x 20mm
Half Wave Voltage at 633nm 220V 220V 220V
Crystal Orientation 45?y-cut 45?z-cut z-cut
Wavelength Range 0.3 - 1.0?m 0.2 - 1.2?m 0.5 - 4.0?m
Windows BK7 BK7 Quartz
Max. Continuous Applied Voltage 250 250 400
Extinction ratio > 100:1 > 200:1 > 200:1
Capacitance 60pf 40pf 60pf
Cell Diameter 40mm 40mm 40mm
Cell Length 110mm 110mm 110mm
Optical Transmission > 85% > 90% > 90%
Connectors ---BNC---
Download drawing

All modulators are normally supplied Dry Nitrogen Filled.

Resonant electro-optic phase modulatorElectro-optic Phase Modulators

For fixed frequency operation electro-optic phase modulators can be designed to operate up to at least 2 GHz.

By making the electro-optic crystal part of a tuned circuit, relatively low drive voltages can be used to achieve up to p radians of phase modulation. For the range 50 MHz to 1 GHz the optical element is made part of a lumped tuned circuit and above 1 GHz the optical element is made part of a re-entrant tuned cavity or the active component in a traveling wave system.

For the tuned circuit arrangements the drive power required from the source is usually less than one watt.

These phase modulators can currently only be supplied without a drive source.

General Specifications for electro-optic phase modulators

1. PM50-500 (50 MHz to 500 MHz version)

Outline drawing of phase modulator head
Outline Drawing of Phase Modulator Head

Optical wavelength range 600 - 1300 nm
(Lithium Tantalate)
Crystal Configuration Brewster cut or
ar/ar normal incidence rod
Aperture 2mm
RF Drive power 2 watt maximum for p radians
Tuning range of optical head ? 15% of center frequency
Voltage gain from tuned circuit ~ 100
Input impedance of head ~ 50 Ω
Note: These are typical specifications taken from a phase modulator operating at 100 MHz.

2. PM1000-2000 (1 - 2 GHz version)
Optical Wavelength range 600 - 1300 nm
Lithium Tantalate
200 - 600 nm (ADP)
Typical Crystal Configuration 15mm long, 2mm ?rod, ar/ar
Aperture 1.5mm maximum
Tuning range of cavity ? 5% of design frequency
Cavity Q > 100
Cavity design impedance ~ 50Ω
Cavity overall dimensions 50mm ?x 50mm length
(2 GHz version)
Drive Power 0.5 - 2.5 watts

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