In confocal microscopy, a pinhole is used to remove extra light generated outside the focal point on the sample and to improve optical resolution and contrast. However, the amount of light that reaches the detector is reduced by the pinhole. So the detector needs higher sensitivity and lower dark current to achieve a better signal-to-noise ratio, resulting in higher dynamic range and in better contrast between the sample’s structure and the background.
Then how about multiphoton microscopy? Multiphoton microscopy does not require a pinhole like confocal microscopy, and it can observe deeper into the sample. Despite the light not being dimmed by a pinhole, the amount of signal is still very small because the multiphoton absorption process is a phenomenon that occurs with a very low probability. So a detector for multiphoton microscopy requires high sensitivity and low noise performance, just like confocal microscopy.
Hamamatsu offers both PMTs and MPPCs (SiPMs) as detectors in confocal and multiphoton microscopy, but the best detector depends on light intensity, sample thickness, scan speed, and many other factors. Please feel free to contact us regarding the selection of detectors.
A compound-semiconductor photocathode for PMTs is designed to further improve the photocathode’s crystallinity and increase its sensitivity in the visible and near-infrared regions. To produce compound-semiconductor photocathodes, a crystal made of gallium arsenide (GaAs) or gallium arsenide phosphide (GaAsP) is adhered to glass, thinned to several µm thickness, and then reacted with cesium to achieve high quantum efficiency (QE). These compound-semiconductor photocathodes, which achieve high sensitivity, are superior to alkali photocathodes in the following ways:
Figure 1. Typical spectral response curves for PMTs with GaAs and GaAsP photocathodes
As shown in the spectral response graph (Fig. 1), GaAs/GaAsP photocathodes are highly sensitive not only in the visible region but also in the red region (such as at 700 nm and 800 nm), which tends to have a smaller amount of fluorescence.
Although GaAs/GaAsP photocathodes have high QE, their disadvantage in the past was their low damage threshold. However, Hamamatsu has recently improved the durability of these photocathodes, and now offers several PMT modules (Fig. 2) that incorporate the improved photocathodes. Click on a part number below to learn more about these modules.
Figure 3. H15460-40 PMT module with a large 14 mm square effective area
As described in a previous question, multiphoton microscopy obtains signals from a deeper part of the sample. The signals are diffused in the sample, and a detector with a wider field of view is required to collect as much of the signal as possible.
Also, when designing a microscope, it is difficult to balance the field of view, magnification, numerical aperture (NA), etc. For example, if you just want to widen the field of view, you can use a low-magnification objective lens, but this objective lens has a small NA. A detector with a large effective area helps facilitate such designs.
In addition to its larger area, the H15460-40 has a built-in amplifier to reduce noise between the detector and electronic devices, improving the overall sensitivity. This will improve the image contrast.
Table 1. Gating function specifications of H11706-40 and H12056-40 PMT modules
A gating function temporarily switches the distribution of the applied voltage to the dynode, preventing the electrons from moving to the subsequent stage. Please note that the gating function is effective only when the timing of the excess light is known in advance; it has no effect on accidental overexposure to light. See Table 1 for the gating specifications of the H11706-40 and H12056-40 PMT modules.
Hiro Furuhashi is a marketing engineer in Hamamatsu’s San Jose, CA, office. He had been designing PMT modules for 9 years before moving to the US from Japan in 2019. He currently conducts market research on microscopy, in vitro diagnostics (IVD), and flow cytometry (FCM), and he also provides technical support as a PMT and PMT module specialist. He is a very active person, loves traveling, loves sports particularly surfing, and goes to the beach to surf almost every weekend.
It looks like you're in the . If this is not your location, please select the correct region and country below.
You're headed to Hamamatsu Photonics website for US (English). If you want to view an other country's site, the optimized information will be provided by selecting options below.
For modern websites to work according to visitor’s expectations, they need to collect certain basic information about visitors. To do this, a site will create small text files which are placed on visitor’s devices (computer or mobile) - these files are known as cookies when you access a website. Cookies are used in order to make websites function and work efficiently. Cookies are uniquely assigned to each visitor and can only be read by a web server in the domain that issued the cookie to the visitor. Cookies cannot be used to run programs or deliver viruses to a visitor’s device.
Cookies do various jobs which make the visitor’s experience of the internet much smoother and more interactive. For instance, cookies are used to remember the visitor’s preferences on sites they visit often, to remember language preference and to help navigate between pages more efficiently. Much, though not all, of the data collected is anonymous, though some of it is designed to detect browsing patterns and approximate geographical location to improve the visitor experience.
Certain type of cookies may require the data subject’s consent before storing them on the computer.
This website uses two types of cookies:
There are two ways to manage cookie preferences.
If you wish to restrict or block web browser cookies which are set on your device then you can do this through your browser settings; the Help function within your browser should tell you how. Alternatively, you may wish to visit www.aboutcookies.org, which contains comprehensive information on how to do this on a wide variety of desktop browsers.
Occasionally, we may use internet tags (also known as action tags, single-pixel GIFs, clear GIFs, invisible GIFs and 1-by-1 GIFs) at this site and may deploy these tags/cookies through a third-party advertising partner or a web analytical service partner which may be located and store the respective information (including your IP-address) in a foreign country. These tags/cookies are placed on both online advertisements that bring users to this site and on different pages of this site. We use this technology to measure the visitors' responses to our sites and the effectiveness of our advertising campaigns (including how many times a page is opened and which information is consulted) as well as to evaluate your use of this website. The third-party partner or the web analytical service partner may be able to collect data about visitors to our and other sites because of these internet tags/cookies, may compose reports regarding the website’s activity for us and may provide further services which are related to the use of the website and the internet. They may provide such information to other parties if there is a legal requirement that they do so, or if they hire the other parties to process information on their behalf.
If you would like more information about web tags and cookies associated with on-line advertising or to opt-out of third-party collection of this information, please visit the Network Advertising Initiative website http://www.networkadvertising.org.
We use third-party cookies (such as Google Analytics) to track visitors on our website, to get reports about how visitors use the website and to inform, optimize and serve ads based on someone's past visits to our website.
You may opt-out of Google Analytics cookies by the websites provided by Google:
We inform you that in such case you will not be able to wholly use all functions of our website.