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Chapter 10: Q66E (page 470)

Question: In a diode laser electrons dropping from the conduction band across the gap, and into the valence band produce the photons that add to the coherent light. The ZnTe laser has a band gap of 2.25 eV. About what wavelength laser light would you expect it to produce?

Short Answer

Expert verified

Answer

The wavelength of the light is 551nm .

Step by step solution

01

Given data

The ZnTe Laser light has a band gap of 2.25eV

02

Concept of the energy of a photon

The energy of a photon is related to the frequency f is, E=hf.

The frequency of a related to the wavelength is, f=cλ.

Here c is speed of light.

From the above two equations the resultant equation is, E=hcλ.

03

Determine the wavelength of laser light 

The energy of a photon is, E=hcλ.

Rearrange the above equation for λisλ=hcE.

Substitute 1240 eV.nm for hc and 2.25 eV for E in above equation.

λ=hcE=1240 eV.nm2.25 eV=551 nm

Therefore, the wavelength of the light is 551nm.

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Most popular questions from this chapter

The diagram shows a bridge rectifier circuit. A sinusoidal input voltage is fed into four identical diodes. each represented by the standard diode circuit symbol. The symbol indicates the direction of conventional current flow through the diode. The plots show input and output voltages versus time. Note that the output voltage is strictly in one direction. Explain

(a) how this circuit produces the unidirectional output voltage it does, and

(b) what features in the output plot indicate that the band gap of the diodes is about half an electronvolt, (It might seem that about one volt is correct, but consider how many diodes are on and in series at any given instant. In fact, although not the usual habit, it might be more accurate to plot the output voltage shifted upward relative to the input.)

Question: - (a) Compare equation (10-11) evaluated at room temperature for a silicon band gap of 1.1 eV and for a typical donor-state/conduction band gap of 0.05 eV.

(b) Assuming only one impurity atom for every 10³ silicon atoms, do your results suggest that majority carriers, bumped up from donor levels. should outnumber minority carriers created by thermal excitation across the whole 1.1 eV gap? (The calculation ignores the difference in density of states between donor levels and bands, which actually strengthens the argument.)

Question: - A semimetal (e.g., antimony, bismuth) is a material in which electrons would fill states to the top of a band the valence band--except for the fact that the top of this band overlaps very slightly with the bottom of the next higher band. Explain why such a material, unlike the "real" metal copper, will have true positive charge carriers and equal numbers of negative ones, even at zero temperature.

As we see in Figures 10.23, in a one dimensional crystal of finite wells, top of the band states closely resemble infinite well states. In fact, the famous particle in a box energy formula gives a fair value for the energies of the band to which they belong. (a) If for nin that formula you use the number of anitnodes in the whole function, what would you use for the box length L? (b) If, instead, the n in the formula were taken to refer to band n, could you still use the formula? If so, what would you use for L? (c) Explain why the energies in a band do or do not depend on the size of the crystal as a whole.

The vertices of a tetrahedron are four vertices of a cube symmetrically chosen so that no two are adjacent. Show that the angle between the vertices of a tetrahedron is 109.5∘ .
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