Herriott Cells Research Articles

Compact low-repetition-rate femtosecond optical parametric oscillators enabled by Herriott cells.

We report the design and characterization of a femtosecond optical parametric oscillator containing an intracavity Herriott cell. Pumped by a 49.16-MHz Yb:fiber laser, the signal wavelength could be tuned over 1440-1530 nm, with the Herriott cell containing 81% of the free-space cavity length required for synchronous operation. We also report a 12.29-MHz OPO using a sub-harmonic pumping approach, extending the Herriott cell OPO concept to low-repetition-rate cavities.

Calculation model of rectangular-like Herriott cell based on folded-optics method

We present a calculation model for rectangular-like Herriott cells (RLHCs), in which a long cylindrical traditional Herriott cell (HC) is transformed into a rectangular-like configuration by introducing two highly reflective plane mirrors. The position formula for two spheric mirrors and two plane mirrors is provided to precisely define the RLHC. The folding effects of RLHCs with 1–8-times folding are evaluated in terms of the cell length, the cell volume, and the total number of reflections. The proposed folded-optics method significantly enhances the utilization efficiency of the mirror surfaces, resulting in a reduction of both physical length and volume when compared to a traditional HC. Importantly, this reduction is achieved while maintaining the same optical path length, and all of these advantages come at a low cost.

In-flight characterization of a compact airborne quantum cascade laser absorption spectrometer

Abstract. Here, we report on the development of a new quantum cascade laser infrared absorption spectroscopy (QLAS) instrument, the Airborne Tropospheric Tracer In-situ Laser Absorption spectrometer (ATTILA), for atmospheric trace-gas measurements on board of the German High-Altitude Long-range Observatory (HALO) aircraft. Its small and light design makes it suitable for airborne measurements up to approximately 150 hPa of ambient pressure (13–14 km). The dual laser instrument can measure several trace gases simultaneously in two 36.4 m path astigmatic Herriott cells with a data acquisition frequency of 1 Hz. We describe the measurement method and the data acquisition of ATTILA and its in-flight performance by focusing on potential sources of influences on the signal, which we investigated with a dedicated test flight during which the instrument sampled from a constant source. We show that linear critical influences associated with challenging movement patterns can be corrected afterwards, while nonlinear limitations can be minimized by appropriate calibration frequencies and integrated time intervals. During the recent aircraft campaign CAFE Brazil (Chemistry of the Atmosphere Field Experiment in Brazil) from December 2022 to January 2023, carbon monoxide (CO) measurements from ATTILA show a good agreement of a R2 of 0.89 with simultaneous CO measurements from an established IR spectrometer for airborne measurements, the TRacer In Situ TDLAS (tunable diode laser absorption spectroscopy) for Atmospheric Research (TRISTAR), at a 10 s time resolution. First dynamical characteristics and tracer distributions of CO and methane (CH4) over the Amazon rainforest can be identified with ATTILA measurements with a total measurement uncertainty of 10.1 % and 17.5 % for calibration gas mixing ratios of 153 and 1990 ppbv and a data accuracy of 0.3 % and 5.5 % for a data acquisition frequency of 1 Hz for CO and CH4, respectively.

Thermal management in quasi-waveguide amplifiers based on Herriott cells

We present a new geometry for laser amplifiers with bulk laser gain media based on the quasi-waveguide property of Herriott cells. A proof-of-principle experiment and numerical simulations of the heat equation indicate a potential advantage in terms of thermal management.

Sub-percent accuracy for the intensity of a near-infrared water line at 10,670 cm−1: experiment and analysis

Laser measurements of the intensity of near-infrared water absorption line at 10,670.1 cm are made using three different Herriott cells. These measurements determine the line intensity with an standard deviation below of 0.3% by consideration of the new geometrically derived formula for the optical path length without approximations. This determination together with the current accepted value lead to an overall uncertainty of 0.7% of the experimentally assessed line intensity which is compared with previous ab initio predictions. It is found that steady improvements in both the dipole moment surface (DMS) and the potential energy surface (PES) used in the theoretical studies lead to a systematically better agreement with the observation, with the most recent prediction agreeing closely with the experiment.

Modeling Herriott cells using the linear canonical transform.

We demonstrate a new way to analyze stable, multipass optical cavities (Herriott cells), using the linear canonical transform formalism, showing that re-entrant designs reproduce an arbitrary input field at the output, resulting in useful symmetries. We use this analysis to predict the stability of cavities used in interferometric delay lines for temporal pulse addition.

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

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.

Multilaser Herriott cell for planetary tunable laser spectrometers

Geometric optics and matrix methods are used to mathematically model multilaser Herriott cells for tunable laser absorption spectrometers for planetary missions. The Herriott cells presented accommodate several laser sources that follow independent optical paths but probe a single gas cell. Strategically placed output holes located in the far mirrors of the Herriott cells reduce the size of the spectrometers. A four-channel Herriott cell configuration is presented for the specific application as the sample cell of the tunable laser spectrometer instrument selected for the sample analysis at Mars analytical suite on the 2009 Mars Science Laboratory mission.

Precise multipass Herriott cell design: Derivation of controlling design equations

Multipass Herriott cells are often designed using the thin lens approximation, which results in approximate dimensions or imperfect patterns due to both spherical aberration and the finite width of the optic. We derive the design equations for exact solutions to the Herriott cell problem. We also show that Herriott cells using spherical mirrors cannot be designed such that multiple concentric beam patterns all meet their reentrant condition. We derive a solution for elliptical mirrors that allows this condition to be met simultaneously for many beams.

Herriott cell interferometry for millimeter-scale plasma measurements

A Herriott cell consists of two concave mirrors positioned on opposite sides of plasma so as to create multiple laser paths through the plasma. Added to a traditional interferometry diagnostic, the Herriott cell multiplies the effective path length through the medium and thereby increases instrument resolution. Previous work used a planar geometry to validate the use of Herriott cells in interferometer applications where the numerous mirror reflections will significantly degrade the phase front quality. The current work extends the Herriott cell capability to a point configuration. In this geometry the multipass beams converge near a single point within the plasma, useful for performing density measurements in very small scale length plasmas. Ray tracing analysis is used to illustrate example measurement geometries attainable with the instrument. It is shown that the configuration results in two convergence points for the laser paths, which somewhat complicates the interpretation of the experimental data. In addition, the multitude of passes through the high density, small scale length passes increases the likelihood for deleterious refractive effects. The diagnostic capability is demonstrated with measurements of the electron and neutral densities in the plasma exhaust of a Micro Pulsed Plasma Thruster. The measurements are validated with similar, lower resolution measurements, obtained using a single-pass interferometer.

Molecular-Gas-Pressure-Induced Line-Shift and Line-Broadening in the ν 2-Band of H 2S

The pressure-induced shift and broadening of H 2S absorption lines in the ν 2-band due to collisions between H 2S molecules and quadrupole molecules, such as O 2, H 2, D 2, N 2, and CO 2, were studied in the spectral region between 1050 and 1325 cm −1. The measurements were carried out using a pulse-driven diode laser spectrometer with two multipass Herriott cells. The data concerning the collisional broadening and shift coefficients, γ and δ, respectively, and their dependencies on the rotational quantum number J″ and the quadrupole moment Q of the molecular perturber are presented for 14 P-branch transitions (3≤ J″≤8,0≤ K a Prime;≤3, 2≤ K c Prime;≤8), 7 Q-branch transitions (7≤ J Prime;≤10, 1≤ K a Prime;≤2, 6≤ K c Prime;≤9), and 18 R-branch transitions (2≤ J Prime;≤11, 0≤ K a Prime;≤4, 0≤ K c Prime;≤11). The broadening coefficients γ were determined with an accuracy to within 2% and shift coefficients δ were determined with an uncertainty of less than 10 −3 cm −1/atm for the majority of lines and broadening gases.

Analysis of hyperboloidal ray envelopes in Herriott cells and their use in laser resonators

By the use of geometric optics and matrix methods an analysis of the spherical mirror Herriott cell is presented. The hyperboloidal beam envelope inside the cell is derived, and equations are given for the position and magnitude of its waist with respect to design parameters. The analysis is then repeated for the cell within a Fabry-Perot resonator. Here the stability condition is derived, and its region of validity is investigated for a range of parameters. Finally a theoretical study of the beam radius distribution at the optics is presented.