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The Red Pitaya is a commercial, affordable FPGA board with fast analog inputs and outputs. This makes it useful for quantum optics experiments, in particular as a digital feedback controller for analog systems. Based on the open source software provided by the board manufacturer, PyRPL (Python RedPitaya Lockbox) implements many devices that are needed for optics experiments with the Red Pitaya. PyRPL implements various digital signal processing (DSP) modules (see features below). It allows to arbitrarily interconnect the available DSP modules and retrieve signal values on timescales below 1 ms. The graphical user interface (GUI) provides a realtime display of the various measurement instruments and allows the easy configuration of DSP signal chains and feedback controllers. At the highest abstraction level, arbitrary feedback sequences can be defined to fulfill tasks as complex as approaching and locking a resonance of a high-finesse Fabry-Perot cavity (tested up to finesse=100,000).
Features
- a two-channel oscilloscope for measurement and diagnostics
- wo arbitrary function generators for waveform synthesis and noise generation
- four proportional-integral-derivative (PID) controllers with up to fourth-order filters for feedback control
- three demodulation modules for the generation of Pound-Drever-Hall-like error signals and the realization of narrow, phase-tunable band-pass filters
- an infinite impulse response (IIR) filter able to realize transfer functions with up to 24 poles and 24 zeros
- a network analyzer for the characterization of analog and digital systems and in-loop tuning of feedback parameters
- a spectrum analyzer for the measurement and minimization of noise in closed-loop systems
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