Design of a new family of narrow-linewidth mid-infrared lasers

Abstract

We describe the design of a new family of high spectral brightness narrow linewidth (NLW) mid-infrared (MIR) lasers --of < 1 MHz anticipated linewidths --with potential for operation at any target wavelength between 2.5 and 9.5 µm. More specifically, we analyze the potential performance characteristics of mid-infrared distributed feedback (DFB) Raman fiber lasers (RFLs) based on π-phase-shifted (PPS) Fiber Bragg Gratings (FBGs) written in appropriately chosen low-phononenergy glass fibers. In particular, we calculate anticipated threshold pump powers for optimal laser designs and pump wavelengths for single frequency (fundamental mode) operation of specific mid-infrared DFB-RFLs operating at chosen target wavelengths, and show that these pump powers can be as low as a few milliWatts for MIR DFB-RFLs fabricated with appropriate low-loss small mode area single mode fibers. As such, we clearly establish the PPS-DFB RFL platform as a very practical approach for constructing a broad range of narrow linewidth MIR coherent sources for numerous applications, including proximal and remote sensing of molecules and various high spectral brightness and long coherence length MIR applications.

Experimental observation of gain in a resonantly pumped Pr3+-doped chalcogenide glass mid-infrared fibre amplifier notwithstanding the signal excited-state absorption

“…Mid-infrared (MIR) laser sources are of great demand in the fields of biomedical sensing, environmental monitoring and free space communication 1 . Particularly, the 3–12 μm wavelength range has attracted significant interest within the MIR region because it covers two of the transparent atmospheric windows, as well as the vibrational resonant bands of several chemical bonds, such as [S-O], [C-H], and [C=O].…”

Design of a Monolithic Low-Threshold Narrow-Linewidth CW Mid-IR Silicon Raman Laser

“…2(a) shows the definition of the design parameters for the pps-WBG based silicon Raman laser (only few periods near the p-phase shift region are shown). The operating principles of Raman lasers based on pps-WBGs are well-established and verified in the context of distributed feedback (DFB) Raman fiber lasers [15,16].…”

“…Using the mathematical framework and methodology for modeling MIR DFB Raman fiber lasers (reported in ref. 16), we have calculated the threshold pump powers (P th,1 ) for operation of a Raman laser at 3150 nm in the fundamental longitudinal mode of the silicon pps-WBG using a 2710 nm pump wavelength. Fig 2(b) shows the calculated contour-plot for P th as a function of k DFB and L DFB, assuming the propagation through the grating is limited by absorption loss (α = 0.011dB/cm) and that the Raman gain (g R ) is 1.0×10 -10 m/W [17].…”

“…Note that although the pps-WBG can also support higher order longitudinal modes (known as side modes), the frequency of these modes are sufficiently far from the fundamental mode (designed to match with the peak Raman gain) to experience enough gain to grow due to the relatively narrow Raman gain bandwidth of silicon which is about 3-4 nm for a 2.71 µm pump wavelength [18]. Therefore, for a moderate range of pump powers above threshold (up to P ~ 10 × P th,1 ), the higher order longitudinal modes of the pps-WBG will not experience enough gain to reach the threshold powers P th,2 needed for the first higher order mode [15,16].…”

“…Using the mathematical framework and methodology for modeling MIR DFB Raman fiber lasers (reported in ref. 16), we have calculated the threshold pump powers (P th,1 ) for operation of a Raman laser at 3150 nm in the fundamental longitudinal mode of the silicon pps-WBG using a 2710 nm pump wavelength. m/W [17].…”