Development and spectral characterisation of ridge DFB laser diodes for Cs optical pumping at 894 nm

Advances in narrow linewidth diode lasers

“…In 2016, the laboratory and the University of Newcastle, Switzerland proposed a RG-DFB laser, using MOVPE secondary epitaxy to construct a 50-nm-thick InGaAsP grating (period of 273.5 nm) in the P-cladding layer. A rib-waveguide DFB laser with a cavity length of 1.5 mm and a width of 4 µm has a laser wavelength of 894.4 nm at 66.4 • C, a laser linewidth of 797 kHz, a laser power of 40 mW at 160 mA, and an SMSR > 50 dB [17]. These values meet the D1 line pumping requirements of Cs atoms in the atomic clock equipment.…”

Methods and setup for spectral characterization of laser diodes for atomic clocks

“…Multiple measurements of the FPR threshold realized after misalignment and re-alignment of the laser beam have shown a good repeatability, below the level arising from the reading uncertainty for the waveplate angle. However, the uncertainty on the reading of the angle of the rotating quarter-wave plate is estimated at ±2°, a value which is taken into account when calculating the FPR threshold uncertainty from equation (2).…”

“…Here we present methods to characterize advanced laser diodes emitting at 780 nm or 795 nm [1] as well as at 852 nm or 894 nm [2], in view of their implementation in Rb and Cs atomic clocks [3,4] and other optical high-precision applications. The characterization consists of the usual parameters (threshold current, slope efficiency, frequency tuning, polarization, and beam geometry) with additional emphasis on spectral parameters that are of highest importance in atomic clock applications, such as amplitude and frequency noises, linewidth and sensitivity to optical feedback.…”