Injection laser, light output

The dissociation laser light between 230 and 305 nm was produced by frequency doubling the output of an optical parametric oscillator (Spectra-Physics MOPO-730) pumped by an injection-seeded Nd YAG... 

When we wish to verify the lasing operation of a new and/or ultra-low threshold device, the non-linear relation in the injection current versus light output characteristics is an easy method of testing the threshold criterion. However, sometimes this is observed even on non-lasing samples owing to the filtering effect and electron-hole plasma emission. Methods used to definitively confirm laser operation for vertical cavity devices are as follows [37] ... 

Figure 3. Light output as a function of current of the injection laser operating at 1.51 pm (at 20 °C). Insert shows quantum-well parameters. (Adapted from Ref. 39.)...

The measurement is conducted by frequency modulating a diode laser by superimposing a radio frequency oscillation, Q, onto the diode injection current. The spectral output of a frequency modulated diode laser, shown at the top of Fig. 3, consists of a carrier frequency, a>c and side band frequencies, cOc H. When the laser is scanned through the wavelength of oxygen absorbance, the amount of light absorption, which is proportional to the gas concentration, is written into the side band frequencies by recording the difference in absorption between the two sidebands. 

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