Calculate critical angel and fundamental gaussian mode, Electrical Engineering

(1) An argon ion laser, emitting light at a wavelength of 488nm with a beam divergence of 150 firad, is used to illuminate the moon.

(i) Assuming the earth-to-moon distance is 3:8_108 m, estimate the diameter of the spot on the moon.

(ii) Calculate the waist of the beam in the laser, assuming that the beam is a fundamental Gaussian mode.

(iii) Suggest a way by which the spot diameter on the moon could be reduced by a factor of 100.

(2) The bandgap of GaAs is 1.4 eV.

(i) Calculate the probability of a valence electron being in the conduction band by thermal excitation at 0°C.

(ii) The donor binding energy in GaAs is 5.8 meV. Calculate the probability of finding a donor electron in the conduction band at 0°C.

(iii) From an electronic point of view, what is the difference between undoped and n-type GaAs?

(3) An optical fibre has a core refractive index of 1.52, and a numerical aperture of 0.12.

Calculate its:

(i) Critical angle.

(ii) Cladding refractive index.

(iii) Maximum acceptance angle in (a) air, and in (b) water (refractive index =1.3)

(4) (i) What is the primary reason that optical fibres are used for communicating information?

(ii) How can you maximise the amount of information transmitted?

(iii)Estimate the bandwidth of a fibre of core diameter 50°m, n1 = 1:50, n2 = 1:49, and length L = 50 km.

(iv) Identify 2 other things that optical fibres are useful for.

(5) The mean power launched into an optical fibre of length 10 km is 150 _W and the average power at the output is 5°W. Calculate the overall attenuation in dB, and the attenuation per kilometre, assuming there are no interface losses.

Each question is worth ten points.

Posted Date: 3/16/2013 5:17:03 AM | Location : United States







Related Discussions:- Calculate critical angel and fundamental gaussian mode, Assignment Help, Ask Question on Calculate critical angel and fundamental gaussian mode, Get Answer, Expert's Help, Calculate critical angel and fundamental gaussian mode Discussions

Write discussion on Calculate critical angel and fundamental gaussian mode
Your posts are moderated
Related Questions
Q. Explain about Common Channel Signalling? Common Channel Signalling (CCS), centralized maintenance and automatic faultdiagnosis and interactive human-machine interface are so

Q. A 100-turn coil in the configuration of is rotated at a constant speed of 1200 r/min in a magnetic field. The rms induced voltage across the coil is 1 kV, and each turn has a le

excitation in an ac generator

Question 1 Explain the construction of telephone network Question 2 What is out-of-band signaling? Explain Question 3 Describe STP (Signaling Transfer Point) Questio

Question: (a) With the help of a clearly labeled diagram explain the functioning of a basic thermocouple. (b) Briefly explain the principle and operation of strain gauges


A three-phase, 5-hp, 220-V, six-pole, 60-Hz in- duction motor runs at a slip of 0.025 at full load. Rotational and stray-load losses at full load are 5% of the output power. Calcul

Connection of Shunt Capacitors at 11 kV Substations 11 kV automatic switched capacitor banks are installed on bus of 33 or 66 kV substations. This has the facility that the re

How DRAM's are different from SRAM's? Why DRAMs are said to use address multiplexing? Ans Dynamic RAM (DRAM) is basically the same as SRAM except that it recollects data f

An audiomessage is band-limited to 15 kHz, sampled at twice the Nyquist rate, and encoded by a 12-bit natural binary code that corresponds to Lb = 212 = 4096 levels, all of which s