Herriott Cell (Multipass Cell) Setup and Configuration (Viewer Inspired)

Herriott Cell (Multipass Cell) Setup and Configuration (Viewer Inspired) | Thorlabs Insights

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In a Herriott cell (Multipass Cell), light reflects multiple times between two concave mirrors. The reflected beams cross the volume between the two mirrors at different angles, tracing out different paths and creating linear, elliptical, or circular spot patterns on the mirrors. To allow the beam to enter and exit the cell, one or both of the mirrors typically has a hole at its center or near its edge. Herriott cells are used in a variety of applications that benefit from folding a long optical path length into a compact space. Gas-absorption spectroscopy is a popular application, since every additional pass of the beam through the sample volume increases the signal-to-noise ratio of the measurement data.
This demonstration begins with a roughly aligned setup, in which one mirror has a hole near its edge and the other has no hole. Both mirrors have the same focal length. A non-polarizing beamsplitter and a pair of irises are used to set the mirror orientations so they are parallel to each other and perpendicular to a line of screw holes in the table. After this procedure is completed, the angular orientations of the mirrors are no longer adjusted. The demonstration then shows how to achieve different reflections patterns on the mirrors by changing the input beam orientation and cell length.
Both the input beam angle and mirror spacing affect the number of reflections the beam experiences before exiting the cell. A special case is when the two mirrors have the same focal length and are separated by a distance equal to the focal length. This configuration always provides six passes through the cell, regardless of the orientation of the input beam. This mirror spacing is used to illustrate the effects of changing the input beam’s pitch and yaw angles, as well as the beam’s X-axis and Y-axis position. In addition, the input beam is aligned parallel to the cell’s optical axis as a starting point. Then, the cell length is adjusted to increase the number of passes through the cell. Further adjustments to the input beam orientation are demonstrated to create linear, elliptical, and circular reflection patterns.
References:
D. Herriott et al., Appl. Opt. 3, 523-526 (1964).
C.G.Tarsitano et al., Appl. Opt. 46, 6923-6935 (2007).
00:00 - Introduction
00:46 - Herriott Cell Overview
02:37 - Mirror Alignment
04:54 - Transfer Laser Input
06:20 - Adjustments at Reference Distance
07:20 - Obtain a Linear Pattern
08:45 - Obtain Elliptical Patterns
09:36- Obtain a Circular Pattern
Components used in this Demonstration Include:
- CM508-200EH4-M02 Gold-Coated Herriot Cell Mirror with Off-Axis Hole, Ø2”: www.thorlabs.com/newgrouppage...
- CM508-200-M02 Gold-Coated Herriot Cell Mirror, No Hole, Ø2”: www.thorlabs.com/newgrouppage...
- KS2 Kinematic Mirror Mount for Ø2” Optics: www.thorlabs.com/newgrouppage...
- XRN25C Linear Translation Stage, 25 mm Travel: www.thorlabs.com/newgrouppage...
-XRN25-RC2 Quick-Connect Stage Platform: www.thorlabs.com/newgrouppage...
- S1FC637 Benchtop 637 nm Laser Source: www.thorlabs.com/newgrouppage...
--P1-630A-FC-1 Single Mode Fiber Patch Cable: www.thorlabs.com/newgrouppage...
- K6XS Six-Axis Kinematic Mount (For Input to Cell Collimator): www.thorlabs.com/newgrouppage...
- KM100 Kinematic Mount (For Mirror Alignment Collimator): www.thorlabs.com/newgrouppage...
- BA2F Flexure Clamping Base (For Input to Cell): www.thorlabs.com/newgrouppage...
- F230FC-B Collimator for FC/PC Fiber Connectors: www.thorlabs.com/newgrouppage...
- AD11NT Unthreaded Adapter (Collimator to Mount): www.thorlabs.com/newgrouppage...
-SM1D12C and SM1D12D Irises with Ring Actuators: www.thorlabs.com/newgrouppage...
- LMR1 Mount (for Iris): www.thorlabs.com/newgrouppage...
- CM1-BS013 Cube-Mounted Non-Polarizing Beamsplitter: www.thorlabs.com/thorproduct....
- BE1R Magnetic Pedestal Base Adapter (For Beamsplitter): www.thorlabs.com/newgrouppage...
- Post Collars: www.thorlabs.com/newgrouppage...
- BHM3 Magnetic Ruler: www.thorlabs.com/newgrouppage...
For more photonics how-to videos, visit www.thorlabs.com/newgrouppage...

Пікірлер: 9

@TushhsuT 10 ай бұрын

I actually have aligned it once (or rather participated in alignment) about 20 years ago. The only thing - we had both mirrors with an opening and light was escaping in forward direction from a laser. it was also a ring pattern. Now i know it was the Herriott cell. I have actually read the original article tha time, but did not mention authors names. As I remember, we have used the cell to create a compact optical delay unit. Both sensors (PMTs), for signal and trigger, were mounted straight on inputs of an analog 5 GHz oscilloscope to avoid any pulse stretching because of cables resistance and capacitance. So there was no way to make an electrical delay if one wanted to delay one signal over another and we made an optical one.

@hoofheartedicemelted296 8 ай бұрын

Thanks Paul.

@lidarman2 Жыл бұрын

Great video! This is totally coincidental but I am doing this right now in the UV around 265 nm. I am doing it from the concept of injecting light through a mirror with 99% reflectivity. But that said, I am glad to see the alignment technique and going to try to apply it to my set-up. Thank you and as always, thanks for the snacks.

@thorlabs 11 ай бұрын

@lidarman2 That's great! We’d love to hear how it goes and if you come across any alignment tips and tricks you'd like to share - especially considering how working in the UV always has its own unique set of challenges. We’re also happy the Lab Snacks are helping to fuel your work on your Herriott cell!

@drbhavanikumaryellapragada3286 Жыл бұрын

Very good demonstration. However for longer distance, it is difficult. I tried in my lab

@thorlabs 11 ай бұрын

@drbhavanikumaryellapragada3286 It is exciting to hear you tried the approach in your lab, and it is interesting to hear that you applied the technique to a setup where the mirrors were farther apart. The reference cell length in the video (one focal length) always provides six passes through the cell and three reflections on the far mirror. Since this is not the case for other mirror separations, we would love to hear what mirror separation you used and whether you used a different alignment technique!

@drbhavanikumaryellapragada3286 11 ай бұрын

@@thorlabs Dear Sir, Thank you for considering my reply. I have a small lab. I made the setup using a 650 nm CW laser and aluminium mirror which has a cut at 45 degrees angle. The reflected light is collected using a setup which has an OSA to collect the light spectrum. The resultant spectrum gives CNR of 20 dB dynamic range. I am trying to get still more but it was not possible. That's why I informed you that it is difficult for longer ranges. With best regards

@ezdeezytube 7 ай бұрын

Can this be done across a 3 meter distance between mirrors? If so, what is the maximum possible number of reflections potentially possible?

@thorlabs 6 ай бұрын

@ezdeezytube It is possible to have a 3 m long Herriott cell. Equations provided in the paper by Tarsitano et al. (referenced in the description) are useful for calculating the total number of reflections provided by a particular Herriott cell setup. Total reflections of several hundred are generally possible under ideal conditions. However, several non-ideal parameters can make it difficult to predict the maximum number of reflections. One is the absorbance of the medium between the mirrors, and another is the reflectivity of the mirrors. Both attenuate the beam with each pass through the cell, and eventually signal power will be too low to be useful.