Widely wavelength tunable fast intensity-modulated light source for biophotonic applications

Abstract

High modulation depth, fast (megahertz to gigahertz), intensity-modulated light sources of various wavelengths within the 0.7-1.35 μm bio-penetration window are highly desirable for many biophotonic diagnosis systems. In this Letter, we present a novel scheme of a wavelength tunable, ultra-broadband light source which simply consists of a pump laser, a nonlinear fiber, and demodulation circuits. The working wavelength range of the light source is from 0.7 to 1.35 μm which covers a vast part of the bio-penetration window, and its modulation frequencies extends from tens of megahertz to gigahertz. The performances of the proposed light source in either working wavelength range or modulation frequency bandwidth are much superior to any typical laser diodes or solid state lasers currently employed in the frequency-domain or other biophotonic utilization. The wide applicability of this novel light source in diverse biophotonic applications can be observed from our carefully designed diffused optical spectroscopy phantom measurement.

Review of recent advances in frequency-domain near-infrared spectroscopy technologies [Invited]

“…In addition to the new detectors, investigations have also been carried out on new types of light sources. In 2017, Huang et al [ 32 ] proposed a wavelength-tunable, ultra-broadband light source for FD-NIRS system. A compact Yb-YAG laser (Mikan, Amplitude System, France) was implemented as the light source, with a 1.03 central wavelength, a 250-fs pulse width and a 54.77 MHz basic repetition rate.…”

“…In many existing FD-NIRS systems [ 19 – 21 , 23 , 25 , 27 , 29 , 30 , 32 , 34 , 35 , 39 – 41 , 44 – 48 , 51 , 52 , 54 , 56 – 58 , 60 – 62 , 65 ], Edge-Emitting Lasers (EELs) have been widely applied as light sources. In an EEL, light is emitted from the edge of the substrate, and an EEL offers relatively high power density and wall-plug efficiency, and good beam uniformity [ 78 ].…”

“…Of note, the source powers in all the discussed devices [ 19 – 21 , 23 , 25 , 27 , 29 , 30 , 32 , 34 , 35 , 39 – 48 , 50 – 52 , 54 , 56 – 58 , 60 – 62 , 65 ] are expected to meet the skin safety limits (i.e. maximum permissible exposure) suggested by IEC 60825 standard [ 80 , 81 ].…”

“…In comparison, thanks to their relatively small size and in-built amplification, another type of photodetectors, APDs, have been widely employed in FD-NIRS devices [ 18 – 25 , 32 – 35 , 37 – 51 , 53 , 54 , 56 – 68 ]. In particular, APDs possess internal gains of 10 2 - 10 3 and low dark currents (∼0.1-100 nA at 25 °C [ 84 ]), providing exceptional SNRs.…”

Wavelength Tunable Ho3+-Doped ZBLAN Fiber Lasers in the 1.2-<inline-formula> <tex-math notation="LaTeX">$\mu$ </tex-math> </inline-formula>m Wavelength Region

“…Q-switched and mode-locked Ho 3+ -doped ZBLAN fiber lasers have also been successfully demonstrated with passive modulation devices including graphene, carbon nanotube, semiconductor saturable absorber, and a nonlinear polarization rotation (NPR) technique [14]- [17]. However, all these lasers operate at one specific wavelength which may limit their application in scenarios where wavelength tuning is desirable [2], [18].…”