Articles

Archive · RSS

Photomultipliers: There's a Lot to Love

June 23, 2021 — updated November 11, 2021

Placeholder for a PMT article on photon counting, low-current analogue mode vs. MPPCs, and the high linearity version

What Photodetector Should I Use for Application 'X'?

June 23, 2021 — updated November 11, 2021

We often get asked questions like, “How do I know what photodetector is best for (application X)?” For some values of X, it’s pretty simple: if you’ve got milliwatts of visible light, use a silicon PIN photodiode and an ordinary transimpedance amp (TIA) made from an op amp or (for faster things) a packaged 50-ohm RF amplifier. It’s usually easy to verify that you’re in the shot noise limit—if your photocurrent drops more than 50 mV across its load impedance, you’re there. (*)

Silicon Photomultiplier (SiPM, MPPC) System for Cathodoluminescence

January 30, 2020

In How We Work, we gave an overview of how we build instruments, from the initial feasibility calculation (or photon budget) to delivery of the first production units.

Each project is different, of course, but there are common themes. Here’s a description of these steps from our most recent one at this writing (late January 2020), which is a low-cost cathodoluminescence detection system for use in scanning electron microscopes (SEMs).

Photon Budget

Cathodoluminescence Principles

A SEM works by scanning a tightly-focused beam of high-energy electrons (1 keV - 30 keV) across a sample, and looking at the stuff that comes out. For ordinary imaging you usually look at backscattered and secondary electrons, but there are other modes. For instance, you can get a lot of information about the sample’s chemical composition by looking at the x-rays it emits. Most samples will also emit some amount of light, a process called cathodoluminescence .

How We Work: An Example

January 27, 2020 — updated September 7, 2021

At EOI, we’ve been building advanced instruments very successfully for a long time. One reason for our success is our large inventory of working designs, and another is the way we go about doing it. This post walks through a typical sort of development plan for a challenging customer requirement. Here are the usual steps, in the form of a hypothetical email proposal outline for a fibre-coupled noninvasive glucose sensor similar to this one.
(You can also read about a recent project that went a lot like this, except with a single prototype stage.)

Good Books

December 10, 2019 — updated September 7, 2021

Classic Books On Electro-Optics and Circuits In Softcopy

There’s also the 100 Good Books

list from Building ElectroOptical Systems

Books on Electro-Optics

  1. Photomultipliers: Their Cause And Cure Part 1
  2. Photomultipliers: Their Cause And Cure Part2 And Front Matter
  3. RCA Photomultiplier Handbook
  4. RCA Electro-Optics Handbook (1974)
  5. “The Intensity Interferometer” by R. Hanbury Brown

MIL-HDBK-141: Optical Design

  1. Table of Contents through Chapter 6 (pdf)
  2. Chapters 7 through 12 (pdf)
  3. Chapters 13 through 16 (pdf)
  4. Chapters 17 through 20 (pdf)
  5. Chapters 21 through 23 (pdf)
  6. Chapter 24 through Index (pdf)

And, courtesy of the good folks at Any2DJVU: