We report on an External Cavity Diode Laser (ECDL) in a hermetically sealed 14-pin butterfly package with a collimated output beam. The laser emits more than 50 mW at a drive current of 165 mA and the emission wavelength can be tuned between 460.74 nm and 460.97 nm. The maximum mode-hop-free tuning range measures 26 GHz. The laser consists of a GaN-based gain chip, which is collimated by an aspheric lens. Behind the lens, a Volume Bragg Grating (VBG) stabilizes the laser emission to the target wavelength of around 460.8 nm, which can therefore be used for laser cooling or trapping of strontium without the need for frequency-doubling. Inside the butterfly package, the laser diode is soldered on a ceramic submount and mounted on an optical work bench together with the aspheric lens and the VBG. The optical work bench is temperature stabilized by a Thermoelectric Cooler (TEC) in combination with a thermistor. In frequency noise measurements of the packaged laser, we measured a white noise level of 1.29 MHz. This demonstrates a reasonable stabilization of the emission wavelength of the gain chip via the VBG. By further improvements of the ECDL we expect that a linewidth ⪅ 1 MHz can be achieved. This development paves the way for compact, blue laser diodes with a narrow linewidth for quantum technology, spectroscopy, and sensing.
For compact spectrometers with high resolution and especially for Quantum Technology (QT) of the second generation, compact, portable, and long-term stable systems are a prerequisite for the breakthrough of the technology. In this paper, we demonstrate a miniaturized external-cavity diode laser (miniECL), which is frequency stabilized with a Volume Bragg Grating (VBG), and a miniaturized fiber-coupled tapered amplifier (miniTA). Both devices feature a collimated output beam and are integrated in a hermetically sealed 14-pin butterfly module. Due to the external cavity design and a robust packaging process, the miniECL has a linewidth below 350 kHz with an output power ⪆ 80 mW at 670 nm, 770 nm, 780 nm, 852 nm, and 894 nm. These wavelengths correspond to the D1 and D2 transitions of Li, the D1 transition of K, the D2 transition of Rb and the D2 and D1 transition of Cs, respectively. Hence, the miniECL is perfectly suited to excite atomic transitions. In addition, the miniECL can be used as a seed laser for the miniTA, which amplifies its output power to 1.5 W - 3.0 W with excellent beam quality (M2 between 1.3 and 1.7 and beam divergence ⪅ 3 mrad), while maintaining the narrow linewidth of the seed laser. The amplification bandwidth of the miniTA matches with the emission wavelength of the miniECL, which enables extremely compact Master Oscillator Power Amplifier (MOPA) setups.
We report the latest development of a polarization-maintained fiber-coupled miniaturized external cavity diode laser (ECDL) at 780 nm with a narrow linewidth of less than 100 kHz and optical isolation of higher than 60 dB integrated into a temperature controlled hermetically sealed industrial standard butterfly package. Combined with a fiber-coupled tapered amplifier, this provides a plug and play low SWaP (Size,Weight and Power consumption) “Master Oscillator Power Amplifier”-system, without the need of additional bulky optical free-space components such as optical faraday isolators and time-consuming optical alignment. In addition to robustness and high stability, we were able to combine the narrow linewidth of the external cavity diode laser and the high output power of the amplifier in the footprint of only two butterfly packages. Output powers higher than 25 mW of the seed laser ex-fiber are sufficient to saturate the tapered amplifier to reach optical powers of more than 3 W with high beam quality and integrated beam collimation. The integrated isolators with isolation greater than 60 dB assure a stable operation and no disturbance of the seed laser by the tapered amplifier. Furthermore, we used an additional optical resonator to reduce the linewidth to less than 10 kHz using an electronic stabilization scheme according to the Pound-Drever-Hall technique with electronics provided by TOPTICA Photonics AG.
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