Liquid Instruments Moku:Go

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Summary

User interface

Upper user interface

Displays the processing chain and principal controls of the Laser Lock Box.

Lower user interface

Displays parameter control panels for locking stages, oscilloscope, and data logger.

Additional tools

File Manager

Download saved data from Moku:Go to a local computer with optional file format conversion.

File Converter

Convert Moku:Go binary (.li) files to .csv, .mat, or .npy formats.

The Moku:Go Laser Lock Box is a versatile instrument designed to stabilize laser frequencies to a reference cavity or atomic transition, employing high-performance modulation locking techniques. It is engineered to assist in both frequency stabilization, where the locking system steers the laser frequency to match a reference, and frequency tracking, where the reference frequency is forced to follow the laser frequency. This device offers a compact setup, streamlined acquisition, and robust diagnostic features, simplifying the process of setting up and characterizing laser locking systems.

Function Description:

The core function of the Laser Lock Box is to provide precise control over laser frequency. It achieves this through a sophisticated processing chain that includes signal input, scan configurations, modulation, digital filtering, and cascaded PID controllers. The device can demodulate input signals using various reference oscillators, including an internally generated modulation signal, an independent internal reference, a direct external reference, or an external phase-locked loop (PLL). The PLL mode is particularly useful for locking to external references, offering configurable bandwidth and the ability to multiply or divide the reference frequency. For applications that do not require modulation, such as DC locking or fringe-side locking, a "None" demodulation option is available.

The instrument incorporates two cascaded PID controllers—a fast controller and a slow controller—which can be graphically configured. These controllers provide comprehensive control over proportional, integral, and derivative gain profiles, along with saturation levels for integral and derivative components, with real-time updates to the transfer function. This allows for fine-tuned control over the laser's frequency response.

A key feature is the "staged locking" concept, which enables a user-defined locking process. This allows for quick and reliable locking to any zero-crossing on the demodulated error signal. The "Lock Assist" feature further enhances this by automatically configuring trigger settings to synchronize oscilloscope traces with the scan waveform, and adjusting the output offset to engage the first available locking stage.

Usage Features:

The Moku:Go Laser Lock Box features a user-friendly interface divided into upper and lower screen sections. The upper interface displays the processing chain and primary controls, allowing users to configure signal inputs, scan and modulation signals, and digital filters. Input signals can be configured for AC or DC coupling and attenuation. Scan and modulation signals can be enabled/disabled, assigned to specific output channels, and their shape, frequency, and amplitude can be adjusted.

The digital filter, positioned after the demodulator, is highly configurable, offering various filter shapes (Lowpass, Bandstop, Custom) and allowing users to set corner frequency, filter type (e.g., Butterworth), and order. This helps in removing unwanted signal components from the processing chain.

The lower user interface is dynamic, capable of displaying either the locking stages, an integrated Oscilloscope, or a Data Logger. The locking stages panel allows users to define and manage up to three locking stages, adding actions to each stage that are enabled simultaneously when engaged. Actions can include enabling/disabling scan, fast feedback, and slow feedback, and connecting PID chains to outputs.

The built-in two-channel Oscilloscope enables real-time observation and recording of up to two signals at any point in the processing chain, with sampling rates up to 125 MSa/s. Users can drop probe points along the processing chain to monitor signals, zoom in/out of waveforms, add time/voltage cursors, and configure acquisition settings, timebase, trigger, type, and sensitivity.

The integrated Data Logger allows for long-term recording of signals from up to four probe points, with sampling rates up to 500 kSa/s for two channels or 1 MSa/s for one channel. It supports various acquisition modes (Normal, Precision, Peak Detection), configurable measurement durations, and options to change filenames and add comments. Data can be streamed over a network or saved directly on the Moku:Go device.

Additional tools include a File Manager and File Converter. The File Manager facilitates downloading saved data from Moku:Go to a local computer, with optional file format conversion. The File Converter allows conversion of Moku:Go's binary (.li) format to .csv, .mat, or .npy formats, providing flexibility for data analysis in other software environments.

For Moku:Go M1 and M2 models, a Power Supply control window is accessible from the main menu. This allows users to configure up to four channels (depending on the model) in either constant voltage (CV) or constant current (CC) mode. Users can set voltage and current limits, monitor actual voltage and current readbacks, and toggle the power supply channels on and off.

Maintenance Features:

The manual emphasizes the importance of keeping the Moku:Go device fully updated to ensure optimal performance and access to the latest features. Users are directed to the liquidinstruments.com website for updates and further information.

The main menu provides several utility features that contribute to the device's maintainability and ease of use:

Reset instrument: This option allows users to revert the instrument to its default state, which can be useful for troubleshooting or starting a new configuration from scratch. It's noted that this action cannot be undone.
Save/recall settings: Users can save and load instrument settings, enabling quick restoration of preferred configurations or sharing settings between different setups.
File Manager and File Converter: These tools, while primarily for data handling, also serve a maintenance role by ensuring data integrity and compatibility with external analysis tools. The ability to convert data formats simplifies post-processing and archiving.
Help: The integrated help feature provides guidance on using various instrument features, acting as a readily available resource for users.
Report an issue: Within the File Converter's help menu, there's an option to report a bug to Liquid Instruments, facilitating direct feedback for product improvement and support.
About: This section provides information such as the app version, update checks, and license information, which are crucial for tracking software status and ensuring compliance.

Overall, the Moku:Go Laser Lock Box is designed for both high-performance laser frequency control and user convenience, with a comprehensive set of features for operation, monitoring, and data management.