Title : Incoherent laser radiation
Incoherent laser radiation may be in demand among a variety applications where high directivity and brightness of radiation could be advantageously combined with the absence of speckle patterns conventional for laser radiation. Such patterns arise as a consequence of relatively high coherence of laser radiation and generally play a negative role in many applications. Interference of the incident and reflected beams produces a typical irregular (non-uniform) distribution of the optical electromagnetic field, which is an undesirable phenomenon in many applications.
A great number of publications are dedicated to reduction of the speckle effects. However, all these deal specifically with minimisation of the effect and not with elimination of it altogether. The present research takes up for the first time the possibility of a new type of radiation source, in which salient features of conventional laser radiation (high directivity and brightness) may be accompanied by low coherence. Sources of such unusual radiation may be based on noise-like pulses  that consist of large numbers of sub-pulses with varying amplitude and duration, chaotically positioned within the envelope of a noise-like pulse . Almost random structure of such a pulse must result in minimal (or absence of) interference of electromagnetic field between different parts of the pulse (e.g. between its front and rear portions). Thus, minimal or no speckle pattern should be observable.
The present report considers aspects of practical implementation of an incoherent laser relying on noise-like pulses. Discussed are the most promising cavity configurations and possibilities of adjustable degree of coherence of the output radiation. Further on, the potential problems and bottle-necks of the new type of radiation source are analysed, as is its applicability in specific tasks. The likely period of time necessary for development of commercial incoherent lasers is estimated.
1. M. Horowitz, Y. Barad, Y. Silberberg, Noiselike pulses with a broadband spectrum generated from an Erbium-doped fiber laser, Opt. Lett., v. 22, 799-801(1997). https://doi.org/10.1364/OL.22.000799
2. Y. Jeong, L.Vazquez-Zuniga, S. Lee, Y. Kwon, On the formation of noise-like pulses in fiber ring cavity configurations, Opt. Fiber Technol., v. 20, 575-592 (2014). https://doi.org/10.1016/j.yofte.2014.07.004
What will audience learn from your presentation?
- The report provides knowledge needed to develop an incoherent laser
- Development of a radically new radiation source (low-coherence or incoherent laser) stands to disrupt significantly the application areas of laser radiation
- Development of incoherent laser will enable solutions to long-standing problems of many applications (laser TV, material processing, etc.) related to speckle interference of laser radiation