Broadly tunable femtosecond mid-infrared source based on dual photonic crystal fibers

Abstract

We report a novel scheme of generating broadly tunable femtosecond mid-IR pulses based on difference frequency mixing the outputs from dual photonic crystal fibers (PCF). With a 1.3 W, 1035 nm, 300 fs and 40 MHz Yb fiber chirped pulse amplifier as the laser source, a PCF with single zero dispersion wavelength (ZDW) at the laser wavelength is employed to spectrally broaden a portion of the laser pulses. Facilitated by self-phase modulation, its output spectrum possesses two dominant outermost peaks that can be extended to 970 nm and 1092 nm. A different PCF with two closely spaced ZDWs around the laser wavelength is used to generate the intense Stokes pulses between 1240 - 1260 nm. Frequency mixing the dual PCFs outputs in an AgGaS(2) crystal results in mid-IR pulses broadly tunable from 4.2 μm to 9 μm with a maximum average power of 640 µW at 4.5 μm, corresponding to 16 pJ of pulse energy.

Yb:fiber laser-based, spectrally coherent and efficient generation of femtosecond 13-μm pulses from a fiber with two zero-dispersion wavelengths

“…In conclusion, we have demonstrated a femtosecond 1.3 μm wavelength converter based on efficient, low-noise, and spectrally coherent Stokes band excitation from a TZDW PCF. Seeded by 240-fs pump pulses with soliton order N > 50, the Stokes band exhibits preservation of intensity stability and spectral coherence, which not only shows promising potential toward a robust all-fiber ultrafast source that can be helpful for applications such as biomedical deep-tissue imaging, but also attests to the stability of our reported approaches for mid-IR and RGB generation [10][11][12]. With the maturity in fiber laser technology, average power of the 1.3-μm source can be further scaled up with higher repetition rate source lasers [3,5,15].…”

“…In contrast to these two fiber types, PCF with two-ZDWs (TZDWs) offers a unique route to efficient energy transfer from the pump wavelength to two localized spectral regions beyond either side of the ZDWs [9]. In previous work, we have employed an Yb:fiber amplifier to excite an intense Stokes pulse around ∼1.26 μm from a TZDW PCF for mid-IR differencefrequency generation [10,11] and speckle-free RGB generation [12]. The ∼1.3 μm region is an important optical window for deep-tissue imaging [13] that is traditionally accessed with Cr: forsterite lasers.…”

Interferometric coherence measurement and radio frequency noise characterization of the 1.3 μm femtosecond intense Stokes continuum from a TZDW source

“…Besides these two fiber types, PCF with two-ZDWs (TZDW) offers a unique route to efficient energy transfer from the pump wavelength to two narrow-band continua beyond either side of the ZDWs [12,13]. In previous work, we have used such fiber to excite an intense Stokes pulse around 1.26 μm with a 300-fs Yb:fiber laser for mid-IR difference frequency generation and ultrafast Red-Green-Blue generation [14][15][16][17][18]. The ~1.3 μm spectral region is an important optical window for many applications, including biomedical deep tissue imaging [19] which is in the tuning range of Cr: forsterite lasers.…”

Long wavelength mid-infrared from mixing two colors from a fiber amplifier

“…[10] Recently short pulse fiber laser systems have been used to generate long wavelength MIR through difference frequency mixing, but, the average power is still low. [11,12,13,14,15,16] The MIR is produced by difference frequency mixing a pump pulse from a fiber laser and a tunable second pump pulse, created by focusing some of the fiber laser output into either a photonic crystal fiber (PCF) to make a continuum [11,12] or a strong Stokes pulse [15] or an anomalous dispersion fiber to make a Raman shifted soliton pulse, [13,14] or two PCF's to have both a strong Stokes and a continuum. [16] Typically the maximum power is at a shorter wavelength of ~ 6 µm and the power decreases with increasing wavelength because the nonlinear mixing gives a constant photon conversion efficiency.…”