Problems for Practice

PROBLEMS FOR PRACTICE

1. Find the wavelength of emitted photons from a GaAs laser diode, which has a bandgap of 1.44 eV.

(Ans: 8626 Å) 

2. A CO2 laser source emits light at a wavelength of 9.6 μm and has an output power of 10 kW. How many photons are emitted in each hour by this laser?

(Ans: 1.739 × 1027) 

3. A laser source emits light of wavelength 0.621 μ m and has an output of 35 mW. Calculate how many photons are emitted per minute by this laser source.

(Ans: 6.562 × 1018 photons / minute) 

4. Transition occurs between a metastable state E3 and an energy state E2, just above the ground state. If emission is at 1.1 μm and E2 = 0.4 × 10-19 J, find the energy of the E3 state.

(Ans: 2.2068 × 10-19 J) 

5. If laser action occurs by the transition from an excited state to the ground state E1 = 0 and if it produces light of 650 nm wavelength, what is the energy level of the excited state.

(Ans: 3.0576 × 10-19 J) 

6. Given Eg = 1.43 eV. Find the wavelength of the light emitted by the diode for the given energy gap. Also find the colour of light emitted.

(Ans: λ = 8671.32 Å, IR)