quiz4solution

# quiz4solution - nm Potentially useful equations and data...

This preview shows pages 1–2. Sign up to view the full content.

EE 439 Name_______________________________________ Quiz 4 – Sept 28, 2009 Put your final answers on this sheet and attach any additional sheets behind. You must include your work to get full credit. The light coming from a quantum cascade laser has wavelength of 2 μm. If we assume that the photons are generated by the fall of electrons from the n = 2 level to the n = 1 level of an infinitely deep quantum well, calculate the width of the well. Light with wavelength of 2 μm corresponds to photon energy of 0.62 eV. So we need a well with separation of 0.62 eV between the 1 st and 2 nd levels. E 2 " E 1 = 2 2 # 2 h 2 2 mL 2 " 1 2 2 h 2 2 mL 2 = 3 2 h 2 2 mL 2 . Solving for L L = 3 " 2 h 2 2 m E 2 # E 1 ( ) = 3 2 1.055 \$ 10 # 34 J % s ( ) 2 2 9.11 \$ 10 # 31 kg ( ) 0.62 eV ( ) 1.6 \$ 10 # 19 J / eV ( ) = 1.35

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: nm Potentially useful equations and data: Square-barrier tunneling: T " 16 E U o # E ( ) U o 2 exp # 2 \$ L ( ) ; = 2 m U o # E ( ) h 2 Energy levels in an infinitely deep quantum well: E n = n 2 2 h 2 2 mL 2 p = h E = h "# = c h = 6.63x10 –34 J·s = 4.14x10 –15 eV·s; h = 1.055x10 –34 J·s = 6.595x10 –16 eV·s (Planck’s constant) c = 3.0x10 8 m/s (speed of light in vacuum) k = 1.38x10 –23 J/K = 8.617x10 –5 eV/K (Boltzmann’s constant, not wave number) m = 9.11x10 –31 kg (mass of an electron) q = 1.6x10 –19 C (charge of an electron) ε o = 8.85x10 –12 F/m (free-space permittivity) 1 eV = 1.6x10 –19 J...
View Full Document

{[ snackBarMessage ]}

### Page1 / 2

quiz4solution - nm Potentially useful equations and data...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online