Quantum cascade laser light propagation through hollow silica waveguides

Francis, Daniel; Hodgkinson, Jane; Livingstone, Beth; Tatam, Ralph P.

doi:10.1007/s00340-015-6065-5

Cited by 4 publications

(4 citation statements)

References 24 publications

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“…Another advantage provided by the short measurement time is the lack of speckle noise due to multimode interference that was experienced by, e.g., Chen et al [24]. Although multimode transmission was observed, through speckle patterns measured at the output of the waveguide [35], this was not a significant issue. Since the spectroscopic acquisition is so fast, measurements are made across the laser pulses with durations of the order of hundreds of nanoseconds, no speckle noise associated with intermode interference was observed in the time domain and measurements were instead limited by detector noise.…”

Section: Discussionmentioning

confidence: 99%

“…HSWs offer great potential for low-volume gas cells for use in the mid-IR; however, they can suffer from instability/vibration owing to their multimode nature if coiled [35] or if their bore diameter is more than ∼30 times the application wavelength [18]. Here we use HSW gas cells with a high-frequency (50-100 kHz) modulation technique that minimizes these The values indicate the radial thicknesses of the silica and acrylate of the smallest (300 μm bore diameter) and largest (1000 μm bore diameter) commercially available waveguides from Polymicro Technologies [19].…”

Section: Introductionmentioning

confidence: 99%

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Low-volume, fast response-time hollow silica waveguide gas cells for mid-IR spectroscopy

et al. 2016

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Hollow silica waveguides (HSWs) are used to produce long path length, low-volume gas cells, and are demonstrated with quantum cascade laser spectroscopy. Absorption measurements are made using the intrapulse technique, which allows measurements to be made across a single laser pulse. Simultaneous laser light and gas coupling is achieved through the modification of commercially available gas fittings with low dead volume. Three HSW gas cell configurations with different path lengths and internal diameters are analyzed and compared with a 30 m path length astigmatic Herriott cell. Limit of detection measurements are made for the gas cells using methane at a wavelength 7.82 μm. The lowest limit of detection was provided by HSW with a bore diameter of 1000 μm and a path length of 5 m and was measured to be 0.26 ppm, with a noise equivalent absorbance of 4.1×10^-4. The long-term stability of the HSW and Herriott cells is compared through analysis of the Allan-Werle variance of data collected over a 24 h period. The response times of the HSW and Herriott cells are measured to be 0.8 s and 36 s, respectively.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Low-volume, fast response-time hollow silica waveguide gas cells for mid-IR spectroscopy

et al. 2016

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“…Losses depend on the optics at the input (see Fig. 3), and the optimal optics for an efficient light coupling can be calculated theoretically [9,10]. In case of high-power applications, the hollow waveguides can also be cooled internally by using a simple air cooling through the air-core.…”

Section: Hollow Waveguides (Hwgs)mentioning

confidence: 99%

CO and CO2 laser beam guiding with silver halide polycrystalline fibers and hollow waveguides

Novikov

Usenov

Artyushenko

et al. 2022

XXIII International Symposium on High Power Laser Systems and Applications

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Silver halide polycrystalline infrared (PIR) fibers and hollow waveguides (HWGs) have high transmission at midinfrared wavelengths from 3 to 18 µm. Their applications include a flexible delivery of CO2 and CO laser power. We investigated transmission of PIR fibers and HWGs at different bending radii using CO2 laser radiation and studied the intensity distribution after the distal fiber. The PIR fibers show only a relatively weak decrease in transmission with increasing curvature 1/R or decreasing bending radius R. This is an advantage over hollow waveguides, where transmission decreases sharply with curvature. Disadvantages are high reflection losses at the PIR fiber end faces due to the high refractive index of 2.15 for wavelengths in the mid-infrared region. To reduce these losses, the surface of the fiber end faces must be treated with several special methods including microstructuring or coupling with an antireflective window. The measured near-field and far-field intensity distributions or beam profiles are highly inhomogeneous for both fiber types. For large core diameters of 0.9 or 1 mm, the beam profiles appear to be more homogeneous for the PIR fibers.

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“…Based on IR imaging method, Sampaolo et al [32] demonstrated the QCL beam single mode propagation through Ag/AgI-coated HWGs with a bore size of 200 μm in the spectral range of 5.1∼10.5 μm, and measured the transmission loss at different coupling conditions by changing the coupling lens. Francis et al [33] coupled a 7.8 μm pulsed QCL with Ag/AgI-coated HWGs and verified that a thermal imaging camera could obtain more detailed images of the output intensity distributions from the HWGs. However, the loss of laser transmission by an HWG typically decreases as the transmission distance increases, particularly for a laser beam with a large angle, owing to the gradual reduction in the leakage of the laser power into the cladding of the HWG.…”

Section: Introductionmentioning

confidence: 99%

Quantitative Determination of Loss Properties of Semiconductor Laser Beams Propagating in Hollow Waveguides

et al. 2022

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The loss properties of semiconductor laser beams propagating in hollow waveguides (HWGs) are crucial in several applications. The attenuation coefficient of the distributed feedback quantum cascade laser (DFB-QCL) in the HWG was quantitatively determined by measuring its beam profile and laser power along the length of the HWG. The experimental reliability was evaluated, with measurement uncertainties as low as 2.6% and 0.5% for the full width at half maximum (FWHM) of beam profile and the laser power, respectively. We derived an empirical formula for the attenuation coefficient, which is exponential rather than linear with the length of the HWG. The formula was verified to be highly accurate, with a 76.2% reduction in deviation compared to the data in the datasheet. We propose a new concept for a free optical path (FOP) that depends on the inner diameter of the HWG and the incident angle of the beam. The FOP could be an excellent parameter for designing or optimizing HWG-based sensors.

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Quantum cascade laser light propagation through hollow silica waveguides

Cited by 4 publications

References 24 publications

Low-volume, fast response-time hollow silica waveguide gas cells for mid-IR spectroscopy

Low-volume, fast response-time hollow silica waveguide gas cells for mid-IR spectroscopy

CO and CO2 laser beam guiding with silver halide polycrystalline fibers and hollow waveguides

Quantitative Determination of Loss Properties of Semiconductor Laser Beams Propagating in Hollow Waveguides

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