Terahertz generation by spatiotemporally patternable optical pumping beam


Manipulation of the pulse front tilt intensity profile of an ultrashort optical pulse has immense potential for novel light-matter interaction and control. Among the successful applications demonstrated and most promising involves the generation of intense terahertz pulses with high source brightness. As a result, there has been a need to simplify and advance different noncollinear phase-matching schemes for efficient terahertz waves generation. However, majority of the developed schemes employ diffracting gratings to produce the required pulse front tilt intensity profile, which are inherently dispersive. Since an imaging apparatus is mandatory to achieve the desired pulse front tilt at the crystal position, it is imperative that a pump-pulse-dispersion evasive imaging device at the crystal position be developed.  Recently, the echelon mirror has been seen to yield promising results since it produces a discretely pulse front tilt condition from the specular reflection it offers. Unfortunately, like gratings, echelon mirrors are passive devices that cannot modulate the incident light beam electronically.

Recently, a team of researchers led by Professor François Blanchard at École de technologie supérieure with Kosuke Murate and Mehraveh Javan Roshtkhari in collaboration with Xavier Ropagnol at Insitut national de la recherche scientifique, Énergie, matériaux et télécommunications used a digital micromirror device as an alternative for echelon mirrors or gratings to produce an adaptive pulse front tilt intensity pump profile. To be precise, they demonstrated terahertz generation in a lithium niobate crystal using the pulse front tilt pumping scheme derived from a digital micromirror device chip. Their work is currently published in the research journal, Optics Letters.

Briefly, the research method employed entailed the use of two methods: pulse width duration measurements and terahertz waves generation in lithium niobate, to confirm and exactly fine-tune the pulse front tilt nature of the reflected pump beam on a digital micromirror device chip. In addition, they set a simple demonstration using autocorrelation measurements so as to validate the tilted nature of the pulse front tilt intensity profile.

The authors observed that a clear terahertz wave generation through the pulse front tilt pumping scheme in lithium niobate could be derived from a digital micromirror device chip. Additionally, they confirmed that the echelon mirror equation they had used to generate the pulse front tilt intensity beam profile, could be used for digital micromirror device in zero-order reflection mode. They also noted that the reflections from the micromirrors had the benefit of being dispersion free although diffraction still occurred due to the small size and step height.

In conclusion, François Blanchard and his research team study presented a new scheme for varying an ultrafast optical beam spatiotemporally, going from exhibiting no pulse front tilt to exhibiting a left- or right-hand oriented pulse front tilt. Generally, their results open doors for terahertz emissions with a subwavelength controllable spatial pump beam pattern in a collinear or noncollinear phase matching geometry. Altogether, it is anticipated that the versatility of digital micromirror device to modify electronically the spatial intensity distribution of pulse front tilt intensity beams will spark novel applications that extend beyond terahertz -related domains.

Terahertz generation by spatiotemporally patternable optical pumping beam-Advances in Engineering


About the author

Professor F. Blanchard, Eng., M.Sc., Ph.D. has joined ÉTS in 2015 and he recently obtained the ÉTS Research Chair on terahertz (THz) optoelectronic. Among his research achievements, is an internationally recognized expert in the field of pulsed terahertz (THz) radiation with over 12 years of experience. Furthermore, he also has extensive know-how in non-destructive testing of materials with around 10 years of industrial experience. He has so far accumulated more than 50 publications in THz science, 4 patents, a book chapter and two major review articles. He has contributed significantly in establishing a world reference in high field THz pulse generation using nonlinear crystals, as well as in developing, in collaboration with Olympus Corp., the first real-time near-field THz microscope.

His recent contributions include a multidisciplinary project investigating the near-field visualization and manipulation of terahertz vortex light for selective spoof localized surface plasmon resonances in metamaterials, adaptive optical pulse front tilt derives from a digital micromirror chip and THz characterization of printed electronic devices.


Kosuke Murate, Mehraveh Javan Roshtkhari, Xavier Ropagnol, François Blanchard. Adaptive spatiotemporal optical pulse front tilt using a digital micromirror device and its terahertz application. Optics Letters, Volume 43, Number 9 / 1 May 2018.

Go To Optics Letters

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