Intra Pulse Modulation

The emitted wavelength of a DFB laser is given by the spacing of its Bragg grating and is affected by temperature. In the case of a pulsed lasers, the sudden onset of electrical dissipation will increase the temperature during the pulse and chirping will occur. In the Intra-pulse modulation scheme, this chirp is resolved with a fast detector in order to scan through an absorption line.

The final resolution of this method depends on the scanning rate (which depends on the laser) and the detector’s integration time. The scanning range can extend up to 2.5 cm-1.

For more information, we refer you to this 2003 article from Strathclyde University  published in the Journal of the Optical Society of America B or, more recently, this 2014 Optics Letter from the King Abdullah University of Science and Technology.

Typically this method is used with pulse lengths ranging from 200 ns to 1 us. Not every laser chip can withstand such pulses! If you want to use the intra-pulse method, be certain to specify your demands when placing your order. Extra tests can be performed to ensure that each laser will meet your specifications while using this method.