Third-order random lasing via Raman gain and Rayleigh feedback within a half-open cavity

Area of Science:

• Photonics and Optics
• Fiber Lasers
• Nonlinear Optics

Background:

• Random lasing offers a low-threshold alternative to traditional lasers.
• High-order random lasing is less explored due to cavity complexities.
• Existing cavities often limit spectral features.

Purpose of the Study:

• To experimentally demonstrate third-order random lasing in the 1670 nm spectral band.
• To investigate a novel cavity design for enhanced random lasing.
• To establish a platform for studying high-order random lasing mechanisms.

Main Methods:

• Utilizing G.652 fiber as a distributed reflector and fiber loop mirrors (FLMs) as point reflectors.
• Employing a multi-band wavelength-division-multiplexer to route Raman Stokes components.
• Experimental demonstration and validation using a stationary model for output power calculation.

Main Results:

• Achieved third-order random lasing at 1670 nm with a low pump threshold of 2.45 W.
• FLMs preserved intrinsic spectral features due to their wide reflection bandwidth.
• Reflection efficiency remained invariant with pump power, reducing the lasing threshold.

Conclusions:

• The demonstrated random lasing system is the first of its kind in the 1670 nm band.
• The novel cavity design provides a valuable platform for studying high-order random lasing.
• The findings suggest potential for efficient, low-threshold fiber-based random lasers.