thorlabs-powermeter-linux

Thorlabs PM16, PM160, PM100 and PM400 optical power meters on Linux, using the kernel's usbtmc driver. No VISA, no vendor DLL. Comes with a command line tool and a desktop app that does what Thorlabs' Optical Power Monitor does on Windows.

Creator

Warwick Brown
School of Electrical and Information Engineering, University of the Witwatersrand, Johannesburg, South Africa
Email: warwickb10@gmail.com
Homepage: https://www.wits.ac.za/oclab

If you use this in published work, please cite the repository (see CITATION.cff) or acknowledge the Wits OC Lab. Pull requests are welcome.

Install

sudo cp udev/60-thorlabs-pm.rules /etc/udev/rules.d/ && sudo udevadm control --reload-rules
sudo usermod -aG plugdev $USER        # log out and in once
pip install thorlabs-powermeter-linux                # or, before the PyPI release: pip install git+https://github.com/WitsOCLab/thorlabs-powermeter-linux
thorlabs-pm list

For the app (GTK 4 comes from the distribution, so the environment must see system packages):

sudo apt install python3-gi gir1.2-gtk-4.0 gir1.2-adw-1
pipx install --system-site-packages thorlabs-powermeter-linux
thorlabs-pm desktop-install            # puts "Power Meter" in the application menu

Tested on Pop!_OS and Ubuntu 22.04 and 24.04. The app needs libadwaita 1.5 (24.04 or newer); the library and command line do not.

From Python

from thorlabs_pm import PowerMeter

with PowerMeter(wavelength_nm=532) as pm:
    r = pm.read(n=10)                 # {'watts', 'std_watts', 'wavelength_nm', 'dbm', 'n'}
    print(r["watts"], "W")
    pm.configure(auto_range=True)
    pm.zero()                         # store the present reading as the dark level
    print(pm.describe())              # identity, sensor head, calibration date, responsivity

PowerMeter(serial="18090634") picks one meter when several are plugged in. SimPowerMeter has the same interface and no hardware, for tests.

From MATLAB

MATLAB R2022a or newer can call the package directly. Point it at a Python that has the package installed, once per session:

pyenv(Version="/usr/bin/python3");            % or the venv you installed into
pm = py.thorlabs_pm.PowerMeter(pyargs('wavelength_nm', 532));
r = pm.read(int32(10));
watts = double(r{'watts'});
pm.close();

matlab/read_power.m is a working script. Tested with R2026a.

Command line

Command	Does
thorlabs-pm list	meters on the USB bus
thorlabs-pm read -n 10 --wavelength-nm 532	one averaged reading
thorlabs-pm watch	live readings until Ctrl-C (--json for logging)
thorlabs-pm set --auto-range on --zero on	settings and the dark-level zero
thorlabs-pm info	identity, sensor head, calibration date
thorlabs-pm-gui	the app (--sim shows it with a simulated meter, no hardware)

Troubleshooting

• no Thorlabs usbtmc device: check lsusb shows 1313:, that the udev rule is installed and you are in plugdev.
• Readings stop after the meter sat idle: USB autosuspend. The udev rule turns it off for the meter; reload the rules and replug.
• A wrong setting gives an error naming the SCPI command: the code checks the meter's error queue after every write.

Disclaimer

Not affiliated with or endorsed by Thorlabs. "Thorlabs" and the product names are trademarks of Thorlabs, Inc., used here only to say which hardware this works with. The software talks to the meter with the SCPI commands in Thorlabs' own manuals over the standard USBTMC class; it contains no Thorlabs code. It is a laboratory tool, not a safety instrument: do not use its readings for laser safety decisions.

License

MIT. Copyright (c) 2026 Wits OC Lab. See LICENSE.

Acknowledgements

Written for the OC Lab optical computing rig, where it replaced the Windows-only Optical Power Monitor.