Continuous wave Fe²⁺:ZnSe mid-IR optical fiber lasers

Abstract

Today fiber lasers in the visible to near-infrared region of the spectrum are well known, however mid-infrared fiber lasers have only recently approached the same commercial availability and power output. There has been a push to fabricate optical fiber lasers out of crystalline materials which have superior mid-IR performance and the ability to directly generate mid-IR light. However, these materials cannot currently be fabricated into an optical fiber via traditional means. We have used high pressure chemical vapor deposition (HPCVD) to deposit Fe2+:ZnSe into a silica optical fiber template. These deposited structures have been found to exhibit laser threshold behavior and emit CW mid-IR laser light with a central wavelength of 4.12 µm. This is the first reported solid state fiber laser with direct laser emission generated beyond 4 µm and represents a new frontier of possibility in mid-IR laser development.

Recent progress of semiconductor optoelectronic fibers

“…6(b). Lasing at 4.12 µm was observed in this fiber, however, cryogenic temperatures were required owing to short radiative lifetimes and a low slope efficiency of 0.1% was reported [88]. Though, in their infancy and far behind the state-of-the-art for silica-based fiber lasers, these demonstrations clearly show the potential of the semiconductor optoelectronic platform for next generation fiber laser technology.…”

“…Diffusion doping is a common strategy to incorporate transition metal ions in bulk ZnSe, however the uniform concentration region can be produced is about 1 mm and the process is not compatible for fabricating fibers. Considering the volatility and stability in high temperature and pressure (the condition for HPCVD) of various organometallic molecules, it was determined that metallocene bis(cyclopentadienyl)chromium(II) (Cp 2 Cr) and n-butylferrocene are the suitable precursors for Cr and Fe dopant in the HPCVD ZnSe fabrication [79,88]. The mode profile at 1.55 µm of Cr 2+ :ZnSe is shown in Fig.…”

“…It is typical that the glass is silica which is a poor host for the dopants and has a narrow transparency window. This limits the operating power due to multiphoton quenching and nonradiative decay [10,78,88,111]. Semiconductor optoelectronic fibers offer a promising alternative to the traditional fiber laser platform as the host materials can be varied drastically allowing access to new wavelength regions and shorter devices.…”

“…(b) Lasing spectrum of free running Fe 2+ :ZnSe optical fiber at full pump power (600 mW) with cryogenic cooling. Reprinted with permission from Ref [88]…”