Power spectrum of LEDs with known peak emission wavelengths

Four different LEDs are measured using the Oriel 74000 monochromator. Each LED is aligned such that the monochromator slit is inside the viewing angle of the LED. The LED model numbers are given in table 1.

Table 1: Expected & Observed Peaks
Color	Model #	Expected Peak (nm)	Observed Peak (nm)	Difference (nm)
Blue	638-333-2SUBC470	470	330	+140
Green	638-MV8412	565	427	+138
Yellow	638-MC8304	590	441	+149
Red	638-MV8104	660	507	+153

Each LED appears to have a peak emission wavelength 140-150 nm lower than the manufacturer rating. These results would put the blue LED entirely in the UV spectrum, yet the blue LED has a bright blue color when illuminated. The power spectrum for each LED is calculated using the responsivity curve given in figure 5.

Figure 1: Blue LED power spectrum

Figure 2: Green LED power spectrum

Figure 3: Yellow LED power spectrum

Figure 4: Red LED power spectrum

Newport Photodiode Responsivity

Figure 5: Responsivity curve (in blue) for 818-ST2-UV/DB