No abstract

 Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

We propose a cost-effective high-pulse energy supercontinuum (SC) source based on a telecom range diode laser-based amplifier and a few meters of standard single-mode optical fiber, with a pulse energy density as high as ~25 nJ/nm in the 1650-1850 nm regime (factor >3 times higher than any SC source ever used in this wavelength range). We demonstrate how such an SC source combined with a tunable filter allows high-resolution spectroscopic photoacoustic imaging and the spectroscopy of lipids in the first overtone transition band of C-H bonds (1650-1850 nm). We show the successful discrimination of two different lipids (cholesterol and lipid in adipose tissue) and the photoacoustic cross-sectional scan of lipid-rich adipose tissue at three different locations. The proposed high-pulse energy SC laser paves a new direction towards compact, broadband and cost-effective source for spectroscopic photoacoustic imaging.

In this Letter, we demonstrate a high pulse energy and linearly polarized mid-infrared Raman fiber laser targeting the strongest absorption line of C O 2 at ∼ 4.2 µ m . This laser was generated from a hydrogen ( H 2 )-filled antiresonant hollow-core fiber, pumped by a custom-made 1532.8 nm Er-doped fiber laser delivering 6.9 ns pulses and 11.6 kW peak power. A quantum efficiency as high as 74% was achieved, to yield 17.6 µJ pulse energy at 4.22 µm. Less than 20 bar H 2 pressure was required to maximize the pulse energy since the transient Raman regime was efficiently suppressed by the long pump pulses.

Development of novel mid-infrared (MIR) lasers could ultimately boost emerging detection technologies towards innovative spectroscopic and imaging solutions. Photoacoustic (PA) modality has been heralded for years as one of the most powerful detection tools enabling high signal-to-noise ratio analysis. Here, we demonstrate a novel, compact and sensitive MIR-PA system for carbon dioxide (CO2) monitoring at its strongest absorption band by combining a gas-filled fiber laser and PA technology. Specifically, the PA signals were excited by a custom-made hydrogen (H2) based MIR Raman fiber laser source with a pulse energy of ⁓ 18 μJ, quantum efficiency of ⁓ 80% and peak power of ⁓ 3.9 kW. A CO2 detection limit of 605 ppbv was attained from the Allan deviation. This work constitutes an alternative method for advanced high-sensitivity gas detection.

In this work, we present a high pulse energy multiwavelength Raman laser spanning from 1.53 µm up to 2.4 µm by employing the cascaded rotational stimulated Raman scattering (SRS) effect in a 5-m hydrogen (H2)filled nested anti-resonant fiber (NARF), pumped by a linearly polarized Er/Yb fiber laser with a peak power of ~13 kW and pulse duration of ~7 ns in the C-band. The developed Raman laser has distinct lines at 1683 nm, 1868 nm, 2100 nm, and 2400 nm, with pulse energies as high as 18.25 µJ, 14.4 µJ, 14.1 µJ, and 8.2 µJ, respectively. We demonstrate how the energy in the Raman lines can be controlled by tuning the H2 pressure from 1 bar to 20 bar.

We demonstrate a simple and power stable 1.5–10.5 µm cascaded mid-infrared 3 MHz supercontinuum fiber laser. To increase simplicity and decrease cost, the design of the fiber cascade is optimized so that no thulium amplifier is needed. Despite the simple design with no thulium amplifier, we demonstrate a high average output power of 86.6 mW. Stability measurements for seven days with 8–9 h operation daily revealed fluctuations in the average power with a standard deviation of only 0.43% and a power spectral density stability of ± 0.18 d B m / n m for wavelengths <2020