Acousto-Optic Frequency Shifter

Doppler shifts the frequency of input light by an amount equal to the RF drive frequency, but is optimized specifically for this purpose. Typically our frequency shifters will use the anisotropic interaction of the slow shear mode in tellurium dioxide (TeO2). Applications such as interference-based optical techniques require a high extinction ratio between the diffracted and undiffracted beam; this can be achieved with a high-quality optical finish to minimize optical scatter.

We offer standard products with frequency shifts of 40-350 MHz, many of which can be operated in double-pass configurations. In addition we can design for custom frequency shifts where required. Frequency shifters are fabricated using high quality TeO2, grown and polished in-house, for lowest insertion loss and excellent power handling. Other acousto-optic materials are available and may be more appropriate for some applications.

TeO2 based frequency shifters are highly efficient acousto-optic devices, requiring very low drive power to achieve the desired frequency shift. Our designs consume minimal power (generally <100 mW power draw), often allowing us to package the driver with the AOFS for a more compact and power-efficient solution.

Our standard model are below:

1. I-FS040-1.5S2E-3-LE15

• Device: AO Frequency shifter

• Interaction material: Tellurium Dioxide

• RF Drive Frequency: 40MHz

• Operational wavelength: 630 - 680nm

• Reflectivity per surface: < 0·2%

• Minimum optical aperture: 4 x 2·0 mm (horizontal and vertical)

• Active aperture: 1·5mm (vertical)

• Transmission: > 95% @ 633nm

• Maximum diffraction efficiency: > 90% @ 633nm

• Polarisation of input beam: Linear and horizontal with respect housing

• Polarisation state of 1st order: Linear and orthogonal to input and zero order beams

• Zero to 1st order polarisation extinction ratio: > 100:1

• Amplitude Modulation of Diffracted-Order: < -40dB (@40MHz & 80MHz)

• Output Configuration: Diffracted & undiffracted beams split about Input direction.

• Separation (0 to Diffracted-order): > 2º

• RF Drive Power: > 100mW

• Input Impedance: 50W

• RF connector: SMA Bulkhead Jack

• RF driver 97-05301-01 (AODR 1080HE-AD-1.0)

2. I-FS040-2.5S2E-M-PP3

• Device: AO Frequency shifter

• Interaction material: Tellurium Dioxide

• RF Drive Frequency: 40MHz

• Operational wavelength: 630 - 680nm

• Reflectivity per surface: < 0·2%

• Minimum optical aperture: 4.0 x 3.0mm (horizontal and vertical)

• Active aperture: 2.5mm (vertical)

• Transmission: > 95% @ 633nm

• Maximum diffraction efficiency: > 90% @ 633nm (TBC)

• Polarisation of input beam: Linear and horizontal with respect housing

• Polarisation state of 1st order: Linear and orthogonal to input and zero order beams

• Zero to 1st order polarisation extinction ratio: > 100:1

• Amplitude Modulation of Diffracted-Order: < -40dB (@40MHz & 80MHz)

• Output Configuration: Diffracted & undiffracted beams split about Input direction.

• Separation (0 to Diffracted-order): > 2º

• RF Drive Power: ≤ 120mW

• VSWR: TBC

• Input Impedance: 50

• RF connector: MHF SMT receptacle

• RF driver 97-05301-01 (AODR 1080HE-AD-1.0)

STBR Series Free Space AO Frequency Shifters

The STBR Free Space Acousto-Optic Frequency Shifter (AOFS) with RF driver is used to modify the frequency of the optical beam. Due to a Doppler shift, the frequency of the diffracted first order optical beam in the AO modulator or AO frequency shifter is shifted in frequency (wavelength) by the acoustic carrier frequency (wavelength). If the incident acoustic wave is introduced in the direction of the incident optical wave, the laser frequency shifts towards the higher side. If the incident acoustic wave is introduced in the opposite direction of the incident optical wave, the laser shifts toward the lower frequency side.

Our STBR AO Frequency Shifter are below:

For the associated RF drivers, please refer to “RF Drivers for STBR series”.

AOFS for Fibre  Sensors M040-8J-F2S

A compact fibre-coupled acousto-optic frequency shifter ideal for use in interferometric fibre sensor systems such as  Mach-Zehnder and laser Doppler configurations.

Available in frequencies from 35 to 45MHz and either up-shift or down-shift. This device operates over a broad wavelength range making it the first choice frequency shifter for distributed  sensor networks.

- Polarization insensitive

- Choice of wavelengths, 1450 to 1650nm

- Choice of operationg frequency, 35 to 45MHz

Spec ificati on

Opt ions

• Frequency: 35 to 45MHz

• Frequency Shift: Up shift

• Wavelength Range: Centred on 1500 to 1580nm

• Fibre Type: Polarisation maintaining, multimode

• Fibre Connectors: Pig-tails for splicig, FC/APC