Frequency stabilized distributed feedback laser diode system at 1.323 μm using the modulated Zeeman effect

Abstract

We present the design of a highly stable, compact system that achieves the frequency stabilization of a distributed feedback laser diode to an excited-state argon transition at 1.323 μm. The argon atomic reference is generated in a miniature hollow cathode lamp. A small a/c magnetic field is used to Zeeman split the transition and both right- and left-circularly polarized light are used to generate the error discriminant signal and cancel laser relative intensity noise. The output does not contain any frequency modulated components and has been measured to have long-term frequency stability of better than 8×10−11 (20 kHz) with the Allan Variance technique.

Nanosecond Channel-Switching Exact Optical Frequency Synthesizer Using an Optical Injection Phase-Locked Loop (OIPLL)

“…4(a) is for OIL only), limited by the speed of the laser current controller (8-ns rise time). This confirms that, as expected, the locking is almost instantaneous and limited by OIL locking bandwidth [8] as the acquisition time is the same whether the PLL path is used or not.…”

“…4 shows the result for switching between 1570 (0 mA on the grating section) and 1529.88 nm (peak tuning current applied to one grating section: 25 mA) at a frequency of 500 Hz (dwell time on each wavelength 1 ms). The measurement was performed with and without the phase-locked loop to see if, as expected, the locking is limited by the OIL [8]. One can also note that to assess the stability of the locking, the Fabry-Pérot was only scanned between 1529.7 and 1529.9 nm.…”

“…By using an atomic transition-locked optical reference, each channel can have an absolute frequency error 20 kHz [8], while the channel frequency spacing is determined by the stability of the microwave reference. We show that the system can hop between specified wavelengths despite 5-K laser submount temperature changes, the widest temperature range for an absolute frequency locking scheme yet reported.…”

A Monolithic MQW InP–InGaAsP-Based Optical Comb Generator

“…This is small enough to not affect the FM operation of the laser and confirm the fact that we did not see any change in the comb spectrum over a similarly long operation of the FM laser. In order to obtain a higher absolute frequency stability, the laser will need to be locked on an atomic or molecular resonance [25].…”