SPONSORED: SPECTROSCOPY
heating and cooling limits. It can also deliver as low as 0.0009ºC temperature stability with its PI control loop for maximum efficiency and precision. Hashley said: “The researchers also utilised the WTC3293 Evaluation Board for the temperature controller, which enables rapid prototyping with easier configuration and operation. Temperature setpoints and limits, as well as proportional gain and integrator time constants, can be easily adjusted with onboard trimpots. Both of these products are small (WTC3243 has dimensions of 33 x 32.5 x 7.9 mm) and match well with the small size of the chip-scale vapour cell in the 3D printed MO package.” There were a few challenges, explained Hashley: “The first was a compact system with error-free alignment. The second was vibration issues affecting alignment as well as thermal isolation between the optical elements in the package for spectroscopy. These challenges were solved with a thermal isolating material used in three- dimensional printing, which allowed precise and accurate
positions of optics of up to 0.1mm inside the compact setup. The package was made from a polylactic acid material, ensuring relatively low thermal conductivity. This way, the temperature of the hot vapour cell is isolated from the laser and other optical elements. The final challenge was obtaining absorption spectra with the design. Achieving stable and repeatable absorption spectra is critical for demonstrating a viable atomic sensor, and researchers were able to perform absorption spectroscopy tests.”
Stable and repeatable absorption spectra The results of this study could have major implications. With a mere 3.5µL volume of hot atomic vapour, the team recorded and analysed absorption spectra over 600 hours of operation. Real-time data acquisition identified peaks with full-width at half-maximum (FWHM) values based on Gaussian fittings. The absorption amplitude and the ratio of detector output to off-resonance background confirmed the strength of the absorption in the atomic vapour medium.
The schematic cross-section of the MO package: 1 – chip-scale vapour cell, 2 – VCSEL laser, 3 – annular magnets, 4 – collimating lens, 5 – ND filter, 6 – photodiode
Future innovation The development and demonstration of a thermally stabilised, tunable VCSEL MO package for absorption spectroscopy on a chip-scale Rb vapour cell represent a significant leap forward in the field of atomic sensors. This meticulously crafted design underwent rigorous testing, achieving stable absorption spectra over extended periods, thus confirming its reliability.
The compact design of
the magneto-optic package, complemented by the temperature control precision of the WTC3243
Temperature Controller, paves the way for future innovation in space- borne sensors and payloads, as well as various other applications where atomic sensors are indispensable. The combination of these technologies could promise a bright future for atomic sensing in diverse fields.
Find out more technical detail about the Laboratory for Electro-Optics Systems project in the latest White Paper by Wavelength Electronics, titled VCSEL Absorption Spectroscopy of Chip-scale Rubidium Atomic Vapor
New White Paper Now online
VIEW FOR
FREE*
VCSEL Absorption Spectroscopy of Chip-scale Rubidium Atomic Vapor
This White Paper details how researchers from the Indian Space Research Organization in Bengaluru, India, developed and demonstrated the absorption spectro- scopic capabilities of a chip-scale Rubidium (Rb) atomic vapour cell using a thermoelectric cooler integrated VCSEL light source in a magneto-optic package.
www.electrooptics.com/white-papers
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