Photons Professor ; Richard Jones By; Okey Gubor & Kennedy Oghayore Mentor Connection 2005

1. PhotonsProfessor ; Richard JonesBy; Okey Gubor &Kennedy OghayoreMentor Connection 2005

2. What is a Photon • The particle composing light and other forms of electromagnetic radiation • The particle has no mass and no charge • It is basically a tiny, brief pulse of light.

3. Electromagnetic Radiation Electromagnetic radiation is energy in the form of a wave produced as a result of the motion of electric and magnetic charges.

4. the electromagnetic spectrum

5. Gamma Rays • Gamma rays have the the highest energy, but the shortest wave length in the electromagnetic spectrum. • Radioactive materials can emit gamma-rays. Some are natural and others are made by man in things like nuclear power plants. The biggest gamma-ray generator of all is the Universe; it makes gamma radiation in many kinds of ways. • That means it does not take a lot of it to hurt a human being.

6. Visible Light • This is the part of the spectrum that our eyes see. Visible radiation is emitted by everything from fireflies to light bulbs to stars, also by fast-moving particles hitting other particles.

7. X-Rays • X-rays have shorter wavelengths than ultraviolet light but longer wavelengths than gamma rays. • Doctors use them to look at your bones and dentists use them to look at your teeth. Hot gases in the universe also emit X-rays. • They are also very harmful in large doses. • The first person that discovered X-rays took an X-ray image of his hand by mistake.

8. Microwaves • Microwaves are electromagnetic radiation with a longer wavelength than visible light. • Microwaves can be used to study the Universe, communicate with satellites in Earth orbit, and cook popcorn. • It does not have high energy, it can be harmful in large doses.

9. Radio Waves • This form of electromagnetic radiation has the lowest frequency, the longest wavelength, and is produced by charged particles moving back and forth. • Radio stations emit radio waves into the air that are received by your radio. Radio waves are also received by T.V.s and cell phones. They are also emitted by other things such as stars and gases in space.

10. Ultraviolet Waves • The Sun is a source of ultraviolet (or UV) radiation, as well as all of the other types. It is the UV rays that cause our skin to burn. Stars and other "hot" objects in space emit UV radiation.

11. Infrared Waves • The heat that we feel from sunlight, a fire, a radiator or a warm sidewalk is infrared. The temperature-sensitive nerve endings in our skin can detect the difference between inside body temperature and outside skin temperature. • Near infrared waves are not hot at all; you cannot even feel them. These shorter wavelengths are the ones used by your TV's remote control.

13. Ways to detect Photons Photons can be detected in many ways: • Eye • Cameras • Satellites but all of these detect billions of photons at a time. What if we want to detect only a few photons at a time? • Dim lighting (faint star or distant galaxy) • Fast shutter speed (fast nuclear reactions) These ultra sensitive detectors include: • Vacuum photomultiplier tubes (PMT) • Avalanche photodiodes (APD) Even though these are very good sensitive detectors, they both have disadvantages that limit their usefulness.

14. Vacuum photomultiplier tubes Photomultiplier tubes (or PMTs) are photon detectors that have high sensitivity and very fast response. They have high internal gain by multiplying the electrons through a sequence of several amplifying stages. This makes them ideal for the detection of extremely dim light or short pulses of light. When about 8 million electrons come out, you can tell that 8 photons went in. The disadvantage of the photomultiplier tube is that they are big and are easily disrupted by magnetic fields.

16. Avalanche photodiodes APDs are silicon photodiodes that have very high internal gain. Incoming photons are absorbed in the silicon, creating electron-hole pairs. When one electron-hole pairs is produced, it triggers a lot of electrons (like an avalanche). They are good because they are small and robust. They can also work in strong magnetic fields. The bad side to that is that the avalanche ends up being the same size, no matter how many photons caused it. Because of this, it cannot replace the PMT in many applications.

18. Hybrid photodiode • combines the best features of the vacuum photomultiplier tube and the avalanche photodiode. • has high gain and linear characteristics of the vacuum photomultiplier tube and the resistance to magnetic forces of the avalanche photodiode • has the compact size of solid-state detectors and an excellent photon counting capability. • In the HPD the accelerated electrons are driven into the silicon sensor and penetrate deep, creating many electron-hole pairs and when that happens, current is produced.

20. Our Experiment To perform our experiment of detecting single photons, we had to get a single-photon sensitive light detector and we decided to use the hybrid photodiode because of its wonderful characteristics. Other materials that we needed for the experiment included • Light-proof black box • LED flasher • Pulse generator • Oscilloscope • 80 V power supply • 12 KV power supply • Signal amplifier • A lot of signal cables/regular cables and a lot of other tools and simple materials that assisted in the completion of this experiment.

21. Amplifier 12 KV 80 V

22. HPD Protective box Black Box

23. LED flasher Box cover

24. K.O Pulser Connection to the LED

25. 12 KV Box 12 KV Power supply

26. Connections Censored 80 V power supply Oscilloscope Multi meter

27. Full Vision

28. Input Light Pulse Output Current Pulse Oscilloscope

29. Okey Gubor Kennedy Oghayore