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VCSELs for Next-Generation Atomic Sensors

This week’s blog post is provided by Pritha Khurana, Product Line Manager, Active Components

A new generation of small low-power atomic sensors, including clocks and magnetometers, are being developed based on MEMS and VCSEL technologies. VCSELs are emerging as the preferred optical source for these sensors given their ability to provide coherent and consistent output at low power over years of continuous operation. Several factors are driving the adoption of VCSELs for these types of sensors, including:

Lower Power and Smaller Size: An all-optical atomic clock based on a modulated VCSEL eliminates the need for an RF cavity, enabling a substantial reduction in size and power consumption while meeting atomic frequency standards. In the case of atomic magnetometers, the benefits are dramatic as well: replacing traditional gas discharge lamp light sources with a VCSEL optical source reduces sensor power consumption by over 50%, or more than 5 W. In addition, the use of smaller vapor cells can lower power consumption by another two orders of magnitude.

Commercial Viability: Two applications, in particular, are driving demand for VCSELs in atomic sensors— 1) atomic clocks because of the high volumes in which they are used and 2) atomic magnetometers because the requirement for high precision supports greater cost margins.

Mass Production: VCSELs are manufactured and tested at wafer level allowing for easier integration and high volume manufacturing. The simpler geometry of the VCSEL beam lends itself to ease of packaging allowing for use of mass production processes and potential wafer level integration.

Simplified Precision: The ability to produce a single linearly polarized circular light beam make VCSELs especially well-suited for atomic sensors. In a VCSEL-based atomic clock, a microwave source is used to lock the VCSEL to a frequency of 4.6 GHz. The VCSEL is then modulated to generate two frequencies whose difference is 9.2 GHz, the exact cesium resonance frequency used to define the time unit of one second. For a VCSEL-based atomic clock based on rubidium, the microwave source locks the VCSEL to 3.4 GHz to generate the rubidium resonance frequency of 6.8 GHz.

The same principles and components are used to create an atomic magnetometer, with the difference that no microwave modulation of the VCSEL is required since the system can be made to self-oscillate at the required frequency. This oscillation is directly proportional to the magnetic field to be sensed.

New Applications: Finally, each of these factors enabled through VCSEL technology – substantially lower power, smaller size, commercial viability, mass production, and simplified precision – are making it possible to introduce precision atomic sensing into an ever-widening variety of exciting new applications.

For more information about the history of VCSEL technology and its role in emerging applications, visit: