Feedback Mach-Zehnder resonator with “reflector:” Analysis and applications in single frequency fiber lasers

Abstract

The authors propose a resonant loop mirror configuration using two couplers and a weak reflecting element in the feedback arm. The analysis is carried out using the signal flow graph method. Narrow band reflection peaks can be produced using a wide choice of parameters. A Vernier effect in the two loops can lead to a tenfold increase in the free spectral range. These properties make the device more versatile than the earlier studied single coupler resonator with “reflector” and enhance its use in single frequency lasing.

Theoretical analysis of feedback high birefringence fiber loop mirror with dramatically enhanced free spectral range

“…Recently, a feedback Mach-Zehnder resonator [7] with a reflector was proposed to increase the FSR, but it may not be sufficiently stable just like the common Mach-Zehnder comb filter for the optical field circulating in two different physical cavities. A common problem with most of the complex-ring approaches is the stringent environmental stability requirement, which makes the compound cavities with large coprime-number length ratio susceptible to destabilization and thus limits the attainable enhancement factor of the FSR.…”

Theoretical analysis of feedback high birefringence fiber loop mirror for application in single-frequency fiber lasers

“…For addressing the cavity-length problem, compound ring structures are designed to select single frequency in comparatively large free spectral range (FSR) by the vernier effect [9]. A feedback Mach-Zehnder resonator [10] with a reflector was also proposed to increase the FSR, but it may not be sufficiently stable just like the common Mach-Zehnder periodical filter since the vernier effect results from two physical cavities. One common problem associated with most of the complex-ring approaches is the high sensitivity to environmental perturbations.…”

Single-frequency fiber lasers based on metal thiophosphites with sub-kHz linewidths

“…[1][2][3][4][5] The most commonly used configurations for SFFLs include the construction of distributed feedback (DFB) fiber lasers, [6][7][8] distributed Bragg reflector (DBR) fiber lasers, [9][10][11][12][13][14] and ring-cavity fiber lasers with ultranarrow-bandwidth filters. [15][16][17] However, the DBR and DFB fiber lasers cannot efficiently absorb the pump power and also need accurate and costly fiber Bragg gratings (FBGs), whilst the ring-cavity fiber lasers have a complex and unstable structure. A major area of research in recent years has been SFFLs built on ring cavities with saturable absorbers (SAs).…”