High frequency optoelectronic oscillators based on the optical feedback of semiconductor mode-locked laser diodes

Abstract

Optical self seeding feedback techniques can be used to improve the noise characteristics of passively mode-locked laser diodes. External cavities such as fiber optic cables can increase the memory of the phase and subsequently improve the timing jitter. In this work, an improved optical feedback architecture is proposed using an optical fiber loop delay as a cavity extension of the mode-locked laser. We investigate the effect of the noise reduction as a function of the loop length and feedback power. The well known composite cavity technique is also implemented for suppressing supermode noise artifacts presented due to harmonic mode locking effects. Using this method, we achieve a record low radio frequency linewidth of 192 Hz for any high frequency (>1 GHz) passively mode-locked laser to date (to the best of the authors' knowledge), making it promising for the development of high frequency optoelectronic oscillators.

Asymmetric dual-loop feedback to suppress spurious tones and reduce timing jitter in self-mode-locked quantum-dash lasers emitting at 155 μm

“…Reduction in timing jitter occurs due to suppression of external cavity side-modes relative to single-loop feedback. In the literature [13,14], it was experimentally observed that side-mode suppression was achieved when both feedback delays had a common multiple. This shows that effective suppression in external cavity side-modes is highly dependent on the length of the second loop.…”

“…A major limitation of MLLs for most practical applications is their very high timing jitter and phase noise, as spontaneous emission noise and cavity losses make MLLs prone to broad linewidths and, therefore, substantial phase noise [4]. To improve the timing jitter, several experimental methods such as single-cavity feedback [5][6][7][8], coupled optoelectronic oscillators [9], injection locking [10][11][12], and dual-loop feedback [13][14][15] have been proposed and demonstrated. Of the stabilization techniques demonstrated to date, optical feedback is a promising approach in which an additional reflector creates a compound cavity with a high quality factor, with no need for an external radio frequency (RF) or optical source.…”

“…Recently, a simpler dual-loop feedback technique [13][14][15] without optical/electrical conversion has been demonstrated to improve timing jitter of the MLLs and to filter or suppress the unwanted spurious side-bands. Dual-loop configuration proposed to date [13,14] yields a sub-kilohertz linewidth, but produces additional noise peaks at frequencies resonant with the inverse of the delay time in the second cavity. This is undesirable in many applications where low noise and flat spectra are required, as in frequency comb generation.…”

A Review of Optoelectronic Oscillators for High Speed Signal Processing Applications

“…The resulting phase noise is just above −110 dBc/Hz at a 1 Hz offset. Other OEOs have also been demonstrated using optical injection locking of lasers to generate the RF tone [65]. …”

Optimum stabilization of self-mode-locked quantum dash lasers using dual optical feedback with improved tolerance against phase delay mismatch

“…This dual loop feedback configuration gives sub-kHz linewidth with 38 dB suppression in the fundamental side-mode. A number of experimental [18][19][20][21] and numerical investigations [22] have also been made of the dynamics of modelocked semiconductor lasers subject to dual loop feedback. We note that optimum performance of RF linewidth and timing jitter in dual loop feedback has been very sensitive to small phase adjustments, which limits operation to a narrow parameter space and makes optimum performance vulnerable to environmental change.…”