RF DriversAn RF driver generates an RF signal that is used to generate the acoustic wave within the crystal of an AO device. The frequency and intensity of the applied RF signal will determine how much an optical beam is modulated, deflected, or tuned. G&H offers a wide variety of stable high frequency drivers with analog and digital modulation capability, optimized by application. Explore our new line of flexible Smart Dual drivers, or contact us to discuss a custom OEM design.
A RF driver typically consists of an RF oscillator, a modulation circuit, and a power amplifier which generates an RF signal to drive an AO device. The transducer within the acousto-optic modulator uses the piezoelectric effect to very precisely convert the RF signal to an acousto-optic wave in an interactive optical material at a fixed or variable frequency. An acousto-optic device and its RF driver should be selected as a unit to optimize speed and stability for each application. Additional application-specific features may include first pulse suppression, synchronization, pulse shaping, or multi-channel operation. As our AO product lines expand, we are creating more flexible, adaptive RF drivers with dual analog/digital operation and configurable firmware to accommodate functionality like triggering and temperature control without the need for new hardware. Our OEM designs, in contrast, are optimized to each customer’s application, maximizing performance in the required form factor.
CHOOSING AN RF DRIVERThe needs of the AO device will dictate the choice of RF driver. The primary factors to consider are shown below, though speed, duty cycle, and special functions are also important.
- RF power: ranges from 150 W
- Modulation: digital or analog
- Frequency of operation: may be fixed, variable (linearly swept), or programmable
- Stability: influencing choice of VCO vs DDS when frequency is not fixed
- Number of channels: number of output ports or number of output tones from a single port
- Special functions: pulse-killing, synchronization, etc.
MODULATION: DIGITAL vs ANALOGThe modulation mode determines how the applied RF power is varied, and thus the intensity of diffracted light. In digital modulation, the RF power is applied in an on/off state via an applied TTL signal, thus controlling whether the beam is diffracted. In analog modulation, the RF power is controlled through application of a voltage within a specified range, yielding control over the diffraction efficiency and allowing shaping of that waveform in time.
FIXED vs VARIABLE FREQUENCY DRIVERSFixed frequency drivers provide a single output frequency which is matched to the AO device. Offered from 24-440 MHz, fixed frequency drivers may be controlled via analog or TTL input, some with manually adjustable output RF power. These are used most often for modulation applications. Variable and programmable frequency RF drivers allow active control of output frequency. Voltage controlled oscillators (VCOs) provide a linearly swept (variable) RF drive frequency, and are flexible enough to be used for any AO device. Direct digital synthesizer (DDS) drivers offer programmable frequency. They can create random waveforms from a single, fixed-frequency reference clock, and thus are ideal for pulse shaping and special functions. DDS drivers are software driven, and can be run from a user-friendly interface (a GUI), or controlled directly via computer driver commands. Our high-performance multi-frequency DDS drivers generate up to 8 channels of RF frequencies simultaneously.
SMART DRIVERSSmart drivers allow simple or complex digital waveforms to be synthesized, converted to analog signals, and amplified to drive the AO device. This gives great flexibility; for example, it allows the driver to provide multiple programmable frequencies or to swap freely between multiple, complex, bespoke waveforms.
FREQUENCY AGILITY AND CONTROLG&H offer Direct Digital Synthesizer (DDS) drivers that offer high stability and linearity, with fast switching time and high resolution. They are capable of creating arbitrary waveforms from a single, fixed-frequency reference clock, and thus are ideal for pulse shaping and special functions. DDS drivers can be run from a GUI or via driver commands in two modes: 1) random access, with digital words mapping to specific frequencies, and 2) chirped mode for continuous scanning in frequency increments. DDS drivers are also referred to as DFS (digital frequency synthesizer) drivers.
Our technical support team is available to advise on selection and optimization of RF drivers for specific applications, as well as customization of products for OEM integration.
APPLICATIONS OF RF DRIVERSDriving and control of acousto-optic devices, including modulators, beam deflectors, cavity dumpers, fiber-coupled modulators, frequency shifters, mode lockers, multi-channel modulators, pulse pickers, Q-switches, tunable filters.
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