Miami University

Instrumentation Laboratory Project Page

Project: TA Current and Temperature Control System

Department: Physics

Primary Investigator: Dr. Samir Bali

Purpose: The cooling and trapping of atoms at microKelvin temperatures requires ultra-stable frequency-tunable diode laser systems, operating in single transverse and longitudinal mode with a linewidth < 1MHz. However, these diode laser systems are limited in output power to typically less than 10 milliWatts. If the goal is to attain up to a few Watts of single-mode optical power suitable for state-of-the-art experimentation in laser cooling and atom trapping, one of the best methods currently available is to use a tapered amplifier (TA) chip, which is a semiconductor device that achieves high power while retaining the narrow linewidth and stability of the diode laser.

These tapered amplifier systems are available commercially in a price range of $14k - $47k per unit, depending on choice of center wavelength (650-110nm) and desired output power (0.15 - 2.5W). The IL built a state-of-the-art tapered amplifier systems, along with the driver circuits, at a cost of less than $5k per unit. The systems the IL built rival the commercial units in performance. Detailed plans for the design and construction of these systems are presented in "Design and construction of cost-effective tapered amplifier systems for laser cooling and trapping experiments", J. Kangara, et al., American Journal of Physics, 82 (8), 805 - 817 (2014). This paper is one of 16 papers selected by the American Association of Physics Teachers (see to celebrate the 2014 Nobel in physics.

IL Comment: Researcher required a system that would monitor and control both the current and temperature of a TA (thermal amplifier) diode chip that they are using for their research experiments. Given the high cost of the TA (over $3K each), the electronics in this system need to be robust and reliable to run for extended periods of time.
The design consists of a custom temperature and current control system. For the temperature control system, if the temperature deviates 1 °C above the set point, the current out the TA is taken to 0 Amps immediately (in the order of nanoseconds) to prevent damage to the TA. The output current is controlled via remote set point to a Thorlabs LD3000R current controller. The temperature output is controlled via remote set point to Wavelength Electronics temperature control board.
The researcher is able to monitor the temperature set point, process value, and error between the two. Also, the current set point can be monitored as well.

Cost to researcher: $2382.09 (for 3 systems)

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