Ferdinand-Braun-Institut gGmbH

The FBH presents ongoing research activities in transferring the hybrid micro-integrated concept of GaAs-based narrow-linewidth extended cavity diode lasers (ECDLs) onto a single chip. This novel monolithically-integrated ECDL – (mECDL) is based on an innovated 2-step growth process. The concept can be adopted to realize mECDLs at different wavelengths.

Ultra-narrow linewidth AlGaAs/GaAs-based mECDLs emitting at 1064 nm (for iodine spectroscopy) and 778 nm (for 2-photon rubidium spectroscopy) have already been successfully demonstrated. Monolithic integration increases the thermal and mechanical stability of the lasers and allows for cost-effective production of wafer-level lasers for space-borne applications of quantum photonics.
Further reading

Optical atomic clocks provide the most accurate time measurements available so far and have the potential to benefit basic research as well as improve satellite navigation. For strontium optical atomic clocks, we have developed red-emitting distributed Bragg reflector (DBR) lasers with emission wavelengths from 689 nm to 712 nm. The frequency stability with a record spectral linewidth of only 0.4 MHz makes the lasers suitable for laser cooling, repumping and excitation of the clock transition.

In DBR lasers, a ridge waveguide ensures lateral single-mode operation. Frequency stability and specificity of the emission frequency are enforced by a surface Bragg grating at one end of the laser diode. Incorporating the grating into the chip yields smaller and more compact lasers than comparable systems with external gratings, making DBR lasers ideal candidates for space applications of quantum optical sensors.

The FBH has developed compact fiber-coupled amplifier modules delivering several hundred milliwatt CW output power through polarization-maintaining single-mode fibers. The semiconductor-based amplifier systems are optionally available with nonlinear crystals to achieve visible laser output emission through second harmonic generation. To provide the necessary seed power, any arbitrary fiber-coupled laser source can be used. From only 50 mW input power at 1122 nm, for example, more than 450 mW output power is achieved. With the integrated nonlinear crystal, more than 200 mW output power is provided at 561 nm under the same input power conditions, meeting the requirements, for example, of super-resolution microscopy. All variants share the same butterfly-type packages with a footprint of only 47 x 34 mm² and industrial standard fiber connectors. The concept is not limited to a specific wavelength, and amplified output emission at nearly any wavelength in the range between 630 nm and 1180 nm can be realized. Further reading