Page 64 - Photonics Essentials an introduction with experiments

Photodiodes

58 Photonic Devices

Problems
(Refer to Chapter 11, laboratory exercise 11.1.) In the laboratory, you
will measure experimental data that you will compare to the theoreti-
cal models developed in this chapter. You will first design and make a
sturdy and reusable mount for diode devices, and next measure the
current–voltage (I–V) characteristic in reverse and forward bias. You
will observe the effect of photons on the I–V characteristic.
3.1 In the figure below you will find the spectrum of a photodiode de-
tector. The light source is an incandescent lamp with a silicon
filter in front.

Temp = 300 K
Sensitivity = 100 V
Time constant = 300 ms
Slits = 1 mm
Photoresponse f = 387 Hz
Photo volt probe
Tungsten bulb

2000 1900 1800 1700 1600 1500 1400 1300 1200 1100 100
Photon wavelength (nm)

a. What is the lowest photon energy where detection first occurs?
b. What is the upper photon energy where detection cuts off?
c. What causes the detection to cut off?
d. What effect does second-order transmission of visible light by
the monochromator have on this spectrum?
e. What kind of photodiode is doing the detection, Ge or Si?
3.2 You are working with a silicon photodiode of near unity quan-
tum efficiency (ignoring reflections). To measure the responsiv-
ity you illuminate the photodiode with 1 watt of light at 1000
nm. Your measurement of the photocurrent gives 0.65 amps.

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