APD
February 24, 2021
— updated June 20, 2025
Specifications
| |
|---|
| 3dB Bandwidth | From DC–200 kHz to DC–300 MHz |
| Rise Time | 4ns (highest bandwidth configuration) |
| Gain Control Method | Gain settable by serial or analog voltage. Analog voltage control profile mimics behaviour of similar PMT modules. |
| Detector Type | Hammamatsu S13361/S13362 series or On Semi MicroFC series SiPm |
| Coupling | DC |
| Output Impedance | 50 Ω |
| Dynamic Range | All configurations support analog and photon counting |
| Power Requirements | +5V 100mA, -5V 10mA |
| Signal Output | SMA |
| Applications | Flow cytometry, Microplate readers, TOF Lidar |
In the last year or two we’ve been doing a lot of work aimed at replacing photomultiplier tubes (PMTs) in instruments, using avalanche photodiodes (APDs) and silicon photomultipliers (SiPMs). These devices are arrays of single-photon detectors, so they’re also known as multi-pixel photon counters (MPPCs). Our main application areas include biomedical instruments such as flow cytometers and microplate readers, which have to measure low light levels very precisely but don’t need the ultralow dark current of PMTs. (Follow-on articles will talk about our SiPM work in airborne lidar and SEM cathodoluminescence, as well as on improving the performance of actual PMTs.)
January 25, 2021
— updated August 5, 2022
Internal Developments
In the last year or two we’ve been doing a lot of work aimed at replacing photomultiplier tubes (PMTs) in instruments, using avalanche photodiodes (APDs) and silicon photomultipliers (SiPMs). These devices are arrays of single-photon detectors, so they’re also known as multi-pixel photon counters (MPPCs). Our main application areas include biomedical instruments such as flow cytometers and microplate readers, which have to measure low light levels very precisely but don’t need the ultralow dark current of PMTs. (Follow-on articles will talk about our SiPM work in airborne lidar and SEM cathodoluminescence, as well as on improving the performance of actual PMTs.)
January 27, 2020
— updated January 20, 2022
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 .
