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VCSEL

Vertical-cavity surface-emitting lasers, characterized and qualified in-house. This is the one area where we publish performance results and where product is available today.

Readout

Wavelength

A vertical-cavity surface-emitting laser is the pump source at the centre of a vapor cell sensor. For a rubidium-referenced sensor the number that matters is the rubidium D1 line at 794.98 nm, and our 25 µm mesa, 3 µm aperture devices are built to sit close to it — an etalon check across characterized samples reads 791.5 nm, and thermal tuning moves a single device from 791.035 nm at 24.07°C to 791.315 nm at 30°C. Devices are qualified across a 25°C to 80°C envelope at 0.8, 1.5 and 2.2 mA drive.

VCSEL wavelength versus temperatureA temperature axis from 20 to 85 degrees Celsius and a wavelength axis from 790 to 796 nanometres. A measured trace runs from 791.035 nanometres at 24.07 degrees Celsius to 791.315 nanometres at 30 degrees Celsius. A dashed line marks the rubidium D1 target at 794.98 nanometres. A shaded band marks the 25 to 80 degree Celsius qualification envelope the device is tested across.25°C80°C20406080Temperature (°C)791792793794795Wavelength (nm)Rb D1 target · 794.98 nm791.035 nm @ 24.07°C791.315 nm @ 30°C
Wavelength versus temperature, WaveEye WLM scan of a characterized 25 µm mesa, 3 µm aperture device. An etalon check across characterized samples reads 791.5 nm at 25–80°C, 0.8 / 1.5 / 2.2 mA drive. Target is the rubidium D1 line, 794.98 nm.

A separate, higher-power line of multijunction VCSELs runs at 905 nm and 940 nm for automotive sensing — the same process, a different application and a different target wavelength than the rubidium-referenced devices above.

Characterization

Measured, not assumed

Every die is probed and scanned on an automated setup rather than sampled by hand. That is what makes a wavelength figure a specification instead of a typical value, and it is the same apparatus that supports precise photonic characterization for the rest of the sensor.

The photograph is the measurement in progress: two probes down on a single die, the emitted beam visible on the wafer surface.

Probe needles contacting a VCSEL die under a microscope, with the emitted beam visible on the wafer
Under testA VCSEL die on probe, emitting during characterization.Mesa Quantum photograph
A probe head stepping die to die across a VCSEL wafer, marking each device as it is characterized, in the order the automated scan runs.
Step and repeat The probe head steps die to die across the wafer and marks each device as it is characterized. Drawing, not photograph.