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WorksheetsLaser Principles and Theory Quiz
Total questions: 18
Worksheet time: 39mins
What does laser mean?
Who built the first working laser?
Charles Townes
Theodore Maiman
Gordon Gould
What is the main component of a laser system?
Active medium
Pumping source
Optical Resonator
What is population inversion?
What does the Boltzmann equation determine?
What is the effect of greater population inversion?
What are the three important effects in optical physics?
Stimulated emission
Spontaneous emission
Absorption
Calculate the value of the stimulated emission rate to the spontaneous emission for an incandescent lamp operating at a temperature of 1000 K. It may be assumed that the average operating wavelength is 0.5 μm.
Calculate the stimulated emission rate B21 for a transition at 632.8 nm, an average index of refraction of 1, and spontaneous lifetime tspont = 0.3 μs.
Consider two energy states, E2 = 2.1 eV and E1 = 1 eV. Assume that there are 1*10^16 electron/cm^3 in E1. At a temperature of 1000 K, how many electrons are in state 2?
Consider two energy states, E2 = 2.1 eV and E1 = 1 eV. Assume that there are 1*10^16 electron/cm^3 in E1 and 1*10^15 electron/cm^3 in E1. What temperature is required to create this population distribution in thermal equilibrium?
What happens in a three-level laser where the lower lasing level is the ground level?
The nature of a four-level laser is such that a population inversion is easy to achieve.
The three levels laser systems require a much pumping power.
Requires a very high pumping power because the lower laser level is the ground level.
More than half of the ground state atoms have to be pumped to the upper state.
What is the advantage of the four-level laser?
The low population of the lower laser energy level (E2).
It requires less pumping power.
It can operate continuously.
It is more efficient than three-level lasers.
What condition is called 'population inversion'?
N2 > N1
N1 > N2
N2 = N1
N2 < N1
Estimate the exponential gain constant at line center of a ruby crystal having the following characteristics N2 - N1 = 5*10^17/Cm, g(νo) -1 = 2*10^11 Hz at 300o K, tspont = 3*10^-3 s, ν = 4.326 * 10^10 Hz c/n (in ruby)=1.69* 10^10 cm/s.
What is the threshold population inversion condition for laser oscillation to begin?
Estimate the critical population inversion, using the data typical of 6328 A o HeNe laser. The appropriate constants are t_spont = 10 -7 s, l = 12 cm, 1/g(ν)=10 9 Hz, and R 1 & R 2 = 0.98 n=1.
Consider a HeNe laser system with a gain coefficient of -0.001 cm -1. Calculate the intensity of the laser beam after its first single pass between the resonant cavity mirrors, assuming that the starting beam was from the rear mirror. Calculate the intensity after 5 round trips. Assume that no saturation mechanisms exist, that the starting intensity is 1 pW, that the rear mirror is 100% reflecting, the front mirror is 98.5% reflecting and that the laser is 25.5 cm long.
