We have developed a method for creating a chirped laser pulse (i.e., one characterized by wavelength that changes throughout the duration of the pulse). A pump laser drives a dye cell, which emits a relatively broadband pulse. Light from the dye cell is directed into a spectrograph, which spatially separates the spectral components within the pulse. An array of optical fibers collects the separated light such that each fiber relays a relatively narrowband spectrum from the original pulse. These fibers are of varying lengths, such that these narrowband pulses are separated in time. The far ends of these fibers are coupled into a single fiber, so as to effectively reconstitute the original laser pulse with an imposed temporal chirp.
When performing scientific research or material interaction studies, it is often useful to employ a chirped optical pulse (i.e., a pulse in which the optical spectrum is temporally dispersed). For example, a chirped pulse may be used to record or illuminate an event that occurs during an ultra-short timescale, mapping the progress of the event onto wavelength.
Our method for generating a chirped-like laser pulse may be used in the UV, visible, or near-infrared regions of the spectrum. It employs a pulsed broadband dye laser, a wavelength-dispersing element, and fiber-optic cables of varying lengths that terminate in a recombining fiber or connector, to produce a laser pulse in which wavelength varies over the duration of the pulse. Total temporal and spectral pulse widths can be varied and made longer than previously possible, and can be given arbitrary chirps.
Applications and Industries
The device has application anywhere a temporally longer chirped laser output might be desired or where a chirped output is needed in a specific spectral region. In one exemplary application, the purpose is to illuminate a rapidly (spatially) varying object, thus encoding temporal phenomena onto wavelength for subsequent detection with compatible technology.
- Lower cost and complexity than common dispersive techniques
- Arbitrary pulse lengths and chirp functionality otherwise unavailable
- Broader range of possible spectra