G&H has been manufacturing acousto-optic devices and drivers for nearly 40 years with all aspects of the design and manufacturing process managed internally.
G&H has invested in vertical integration of the design and manufacturing of our entire acousto-optic product line, including crystal growth of lithium niobate (LiNbO3) transducer and tellurium dioxide (TeO2), crystal orientation, cutting and shaping, polishing, anti-reflective (AR) coating, transducer bonding, and packaging.
Controlling these processes enables us to meet our customer’s demands, from custom OEM designs, optimized for a wide variety of applications, to standard products.
Proprietary software, developed by our scientists, enable optimization of design, performance, and budgetary constraints of our AO devices.
A piezoelectric transducer is used to convert electrical power to acoustic power which interacts with the light. We utilize various transducer geometries to create acoustic modes specific to the product type:
- Longitudinal (compressional) acoustic mode is typically used for modulators, frequency shifters, mode lockers, Q-switches and phased array deflectors.
- Shear acoustic mode is used for tunable filters, deflectors and frequency shifters.
Special attention is given to the transducer orientation, providing the lowest electrical to acoustic conversion loss, and allowing for more efficient designs. Matching of the coefficient of thermal expansion to that of the optical substrate maximizes durability over operating temperature ranges.
We offer a wide range of optical materials in our acousto-optic products. These materials enable us to offer products covering wavelengths from the ultraviolet to the infrared.
TeO2 is a common crystal used for acousto-optic devices for the visible through near infrared wavelengths. It is grown by G&H in order to improve quality control of the crystal, minimizing distortion, scatter, and loss of the transmitted light of the final device.
Other materials used, but externally sourced, are fused silica, crystal quartz, chalcogenide glass, germanium, sapphire, and flint glass. All of these materials are oriented, cut and polished by G&H, internally, to meet our customers’ needs.
G&H uses a cold weld metal bonding process to provide a strong, reliable, low-loss attachment of the piezoelectric transducer to the interaction material. Bond layer thickness impacts the operational bandwidth of acousto-optic deflectors and tunable filters.
The electrode element of the acousto-optic device defines how the acoustic field is shaped, providing for the most efficient interaction of light and sound. We use apodized electrodes for maximum efficiency. Phased array electrode designs are used to allow deflectors to achieve a large scan angle with minimal intensity variation.
The electrical connection from the impedance matching PCB to the acousto-optic cell is managed by the use of wirebond wires. Commonly used in the semiconductor packaging, wirebonding allows for a reliable low loss connection resilient to environmental conditions such as shock, vibration, and temperature. Another feature of wirebonding is the minimization of acoustic absorption at the transducer connection points.
All transducers are impedance matched to 50 ohms to allow for testing with industry standard RF test equipment. This also allows the usage of commonly available RF drivers and amplifiers. We utilize RF design software to optimize the impedance match over a wide bandwidth.
Packaging design minimizes thermally-induced wavefront distortion and beam wander during operation. Good packaging is required for a long and reliable transducer life. This is especially important for products using tens of watts of RF drive power.
Thermal analysis software models generate effective designs and methods to remove heat from the AO cell. Decades of experience provides us with package designs with proven track records in actual field applications.
RF Driver Manufacturing Capability
An RF signal is required to drive G&H acousto-optic products. The typical RF signal required is tens to hundreds of MHz with power levels from less than 1 watt to greater than 100 watts.
Our drivers are specifically designed to drive our acousto-optic products, comprising an oscillator, a modulation circuit, and a power amplifier.
Deflectors, tunable filters, and frequency shifters require the use of a variable frequency signal source. In these applications either a voltage controlled oscillator or direct digital synthesizer are used.
Some of our variable frequency drivers also include programmability to allow for customization to specific applications.
Many of our photonic solutions are qualified for space or are currently deployed. We understand how to develop, design, and manufacture for extremes of temperatures, radiation, shock, and vibration. We perform extensive qualification testing during engineering builds and flight hardware qualification.