Phase Modulator for Generating Millejoule-Level, Few-Cycle Laser Pulses
Reference Number: 08-11
Inventor: Zenghu Chang; He Wang; Yi Wu
Background:
Significant effort has been devoted to reduce laser pulse duration while increasing the pulse energy for application in both industry and academic research. Our new technique can produce pulses with much higher energy than previous adaptive pulse compressors and has potential to achieve pulses with single-cycle duration. While the shortest recorded pulse (2.8 fs) does not have enough energy for practical application and high power lasers (30 fs) suffer from narrow bandwidth, by improving the throughput of an adaptive phase modulator and by applying it to a high power hollow-core fiber, we compressed laser pulses to ~5 fs at half-millijoule energy levels. As far as we know, this is the highest energy few-cycle pulse ever achieved by adaptive pulse compressors. The phase controllable, millijoule level few-cycle pulses are a new powerful tool for studying single attosecond pulse generation and performing coherent control in new parameter spaces.
Compared to the most widely used method of pulse compression by chirped mirrors, the adaptive phase modulator used in this invention has a larger bandwidth and high flexibility of phase control because it can be adjusted to cope with the day to day phase variations of the white-light pulses and to compensate the high order phase errors.
Fig. 1 demonstrates the pulse spectra after passing through hollow core fiber and the phase modulator. Fig. 2 shows the MIIPS traces from the different iterations and the final pulse duration. Fig. 3 shows the FROG result to confirm the pulse duration.
Advantages:
- Ability to produce short-duration (5.1 fs), higher-energy (300 µJ) pulses with potential to achieve mono-cycle pulses.
- New Phase modulator design creates higher-energy throughput (50%), easier pulse compression and pulse shaping.
- Modified Multiphoton Intrapulse Interference Phase Scan (MIIPS) simplifies setup and can be used to check correctness of applied phase pattern
Applications
- Coherent control experiments using sub-5 fs pulses
- High field physics
- Biological imaging
- Micromachining
Fig. 1. The white-light spectrum before the phase modulator (blue) and after the phase modulator (red). The inset shows the transform-limited pulses for both spectra.
Fig.2. The MIIPS traces (a=5, ?=7 fs). (a) from the first iteration; (b) from the last iteration; (c) the phase determined by the last iteration and the corresponding pulse duration.
Fig 3. Characterization of the laser pulse by the FROG. (a) The measured FROG trace. (b) The reconstructed FROG trace. (c) The retrieved pulse shape and phase (dashed curve). (d) The retrieved power spectrum and phase (dashed curve) and independently measured spectrum (dotted curve). (e) The FROG frequency marginal (dotted red curve) and the autoconvolution (solid black curve) of the measured spectrum from hollow-core fiber. The FROG error is 0.5%, and the trace is at 256×256 grids.
Patent Status
- PCT application filed in April 2009.
Kansas State University Research Foundation seeks to have discussions with companies that are interested in licensing and/or research collaborations.
Interested parties should contact:
National Institute for Strategic Technology Acquisition and
Commercialization (NISTAC)
2005 Research Park Circle Manhattan, KS 66502
Tel: 785-532-3900 Fax: 785-532-3909
E-Mail: nistac@ksu.edu