In RF-optical heterodyne lock (also known as Pound-Drever-Hall lock), the non-linear frequency discriminator range is given by the frequency of the phase modulating signal. Thus, if the detuning frequency between the laser and the resonator is greater than this modulation frequency, which typically lies in the megahertz range, the error signal is null and the closed-loop cannot operate. Furthermore, for a frequency control loop using some integrators, an out-of-range error signal leads to the saturation of the actuators. In such operation, the laser remains unlocked until a proper action from the user has been carried out. This behaviour becomes problematic with high-finesse cavities because the resulting sensor range is reduced to the resonator bandwidth.
The SMA91 module is able to automatically acquire lock for frequency control systems featuring ultra narrow linewidth cavities. Neither computer nor user actions are required since the module includes its own algorithm. The autolock controller is designed to operate with the high-speed (SMB20) and piezo (SMB30) compensators. It features a thermo-electric cooler (TEC) compensator to provide a third nested loop in order to prevent saturation of the piezo actuator.
Several operating modes are provided to help the user during the tuning phase: for example, it is possible to choose which actuators are engaged when the loop is closed. This feature can be useful to find the right polarity of the error signal.
Like all SM-Series modules, the SMA91 is shipped with the schematic diagrams of its electronic circuitry providing all required information for advanced users. In addition, all C source files of the microcontroller firmware are available for our customers on simple request.
The SMA40 module is a low-phase noise crystal oscillator. The module was designed for use in laser frequency stabilizations where the frequency offset between the laser source and the resonance of the reference cavity requires tight and quick control.
In a Pound-Drever-Hall setup, the SMA40 provides the RF oscillating signals required for the frequency error discriminator. Thus, the module is used both for the phase modulator as well as for the mixer.
Three outputs are available on the front panel. The LO and PM signals are respectively fed to the RF mixer and phase modulator inputs. Their power levels can be adjusted within a 40 dB range using either the respective DC-control voltage or the front panel trimmer. The Reference output is a copy (0-dBm) of the oscillator signal. The phase shift between the LO and PM signals can be controlled over 200 degrees using either the front panel trimmer or the dedicated DC-control voltage. The oscillating frequency is set at the factory between 3 MHz and 30 MHz. Because each output use an RF-isolator, single-ended loads can be
driven without introducing ground-loops.
Like all SM-Series modules, the SMA40 is shipped with the schematic diagrams of its electronic circuitry providing all required information for advanced users.
As you seek solutions to evolving laser control challenges, Sisyph Reference Solutions provide the right combination of hardware and measurement expertise.
In specialized applications, we are ready to work with you to define, develop and integrate your next-generation laser control instrumentation.
The SPS10 power source is designed to supply the SM-Series modules. The low-noise SDC10 converters are used to generate 4 outputs from the +24V input. An on-board oscillator allows synchronization of the DC/DC converters. A reverse input protection and an in-rush current limiter are provided for a safe and reliable operation. The power supply can be mounted in a 3U/14HP rack module.
The SMZ-Series provides general purpose modules for the designers of SM-Series based instruments.
The SDC10 module is a low-noise DC/DC converter operating from a single +24VDC input. It is designed to supply sensitive systems.
To achieve low-noise operation, the SDC10 features a high-frequency DC/DC push-pull converter and a low-dropout voltage regulator. High-frequency operation leads to smaller transformer and filter while the 50% push-pull topology reduces the ripple at both input and output. The on-board PWM oscillator can be synchronized with an external source. A shut-down input is also provided to disable the power switches. Stable output voltage and further ripple attenuation are achieved with the LDO regulator. In addition, the circuitry includes a soft-start function and a current limitation. Since the SDC10 provides an isolated output, the module can easily supply a negative voltage. Two 6-pin connectors allow the module to be plugged into a carrier board.