Dissertation - FTP Directory Listing - University of Surrey

the halogen lamp had to tested with a calibrated photodiode to find the spectrum of the lamp. Theresulting spectrum between 400-800nm is shown in Figure 4.24.6.00E-095.00E-094.00E-09Intensity (Wcm-2)3.00E-092.00E-091.00E-090.00E+00300 400 500 600 700 800 900Wavelength (nm)Figure 4.24 Halogen lamp spectrum results from calibrated photodiode measurementsAs can be seen there are 2 peaks around 650nm and 700nm the signal appears strong enough to bedetected by LAS as on the Aspect system tests were performed down to intensities of a few nW. Thespectrum can be compared to published halogen lamp spectrums to see how accurate these resultsare. A published spectrum is shown in Figure 4.25. Both graphs show a peak around 650nm but therest of the spectrum shape is slightly different but show the same trend. The differences could becaused by the calibration of the photodiode used or if the light intensity wasn’t high enough foraccurate readings, but the general shape of the spectrum appears to match the published spectrumand so should be accurate enough for calculating the quantum efficiency of LAS.62