Standard Protocols
Advanced Techniques
Under development
General Advice
Inspiration
Standard Protocols
Advanced Techniques
Under development
General Advice
Inspiration
"Laboratory Optics" by Peter Beyersdorf is a good resource for learning hands-on techniques for running an optics experiment.
The quantum efficiency of a CNT with absorbing length L«w where w is the FWHM of the gaussian beam can be shown to be:
ηL = (IntPC/e)/[(P/hv)*σ]
ηL is the quantum efficiency times length. IntPC is the spatially integrated photocurrent. P is the laser power, hv the photon energy, and σ the absorbtion cross section per length. This can be interpreted as the total charge extracted per unit time, divided by the number of photons absorbed by the nanotube per unit time. By using the following units:
IntPC - nA/um^2
P - W
hv - eV
σ - um^2/um
We get a result of ηL in units of um.
Important units in calculation:
Defoucsed Photocurrent - nA/mW
Required Measurements
During data analysis
– Integrated Photocurrent from photocurrent image
Scale image axes
Remove offset current and potentially do a FFT
Get integrated photocurrent
– Power
Add Power and OD info
– Absorbtion cross section Part 1: Diameter
First get the diameter by chiral identification of resonant peaks.
Use the diameter in the QE table to get EQE.
– Absorbtion cross section Part 2: ABCS per atom
Quick and dirty: just assume graphene abcs giving x um^2/um off resonance and x um^2/um on resonance
Exact: Get defocused photocurrent at image wavelength
Use NT diameter, peak number, and resonance PC area to calculate the conversion factor.
Calculate ABCS from these two values.
Collaborators in Nijmegen at experts in using fluorescence microscopes.
At OSU we collaborate with Vince Remcho's (Chemistry) for fluorescence microscopy.
To get stable laser power out of a laser diode and good power supplier is needed. For Michael Paul's project we borrowed a Tetronix CPS250 triple output power supply from Bill Hetherington (25V 600mA).
The cheap 532 nm laser diode that Michael used does not have a good beam profile. Two options, buy and expensive laser or couple the laser to a single mode fiber.
eV to nm: 1 eV photon has wavelength 1240 nm.