• Zia, H., Ye, K., Klaver, Y., Marpaung, D. and Boller, K-J. (2023), Ultraefficient on-Chip Supercontinuum Generation from Sign-Alternating-Dispersion Waveguides. Adv. Photonics Res. 2200296. https://doi.org/10.1002/adpr.202200296

  Abstract:

  Fully integrated supercontinuum sources on-chip are critical to enabling applications such as portable and mechanically stable medical imaging devices, chemical sensing, and light detection and ranging. However, the low efficiency of current supercontinuum generation schemes prevents full on-chip integration. Herein, a scheme where the input energy requirements for integrated super-continuum generation are drastically lowered by orders of magnitude is pre-sented, for bandwidth generation of the order of 500–1000 nm. Through sign-alternating dispersion in a CMOS-compatible silicon nitride waveguide, an efficiency enhancement by factors reaching 2800 is achieved. It is shown that the pulse energy requirement for large-bandwidth supercontinuum generation at high spectral power (e.g., 1/e level) is lowered from nanojoules to 6 picojoules. The lowered pulse energy requirements enable that chip-integrated laser sources, such as mode-locked heterogeneously or hybrid-integrated diode lasers, can be used as a pump source, enabling fully integrated on-chip high-bandwidth supercontinuum sources.

• H. Zia, N. M. Luepken, T. Hellwig, C. Fallnich, K-J. Boller, Supercontinuum generation in media with sign-alternated dispersion. Laser and Photonics Reviews (2020).

  Abstract:

  When an ultrafast optical pulse with high intensity propagates through transparent material a supercontinuum can be coherently generated by self-phase modulation, which is essential to many photonic applications in fibers and integrated waveguides. However, the presence of dispersion causes stagnation of spectral broadening past a certain propagation length, requiring an increased input peak power for further broadening. Overcoming such spectral stagnation will be key to achieve practical integrated supercontinuum devices. Here, a concept is presented to drive supercontinuum generation with significantly lower input power by counteracting spectral stagnation via repeatedly alternating the sign of group velocity dispersion along the propagation. The effect is experimentally demonstrated in dispersion alternating fiber in excellent agreement with modeling, revealing almost an order of magnitude reduced peak power compared to uniform dispersion. Calculations also reveal a similar power reduction with integrated optical waveguides, simultaneously with a significant increase in flat bandwidth, which is important for on-chip broadband photonics.

• H. Zia,Enhanced Pulse Compression within Sign-Alternating Dispersion Waveguides. Photonics 2021, 8, 50.

  Abstract:

  We show theoretically and numerically how to optimize sign-alternating dispersion waveguides for maximum nonlinear pulse compression, while leveraging the substantial increase in bandwidth-to-input peak power advantage of these structures. We find that the spectral phase can converge to a parabolic profile independent of uncompensated higher-order dispersion. The combination of an easy to compress phase spectrum, with low input power requirements, then makes sign-alternating dispersion a scheme for high-quality nonlinear pulse compression that does not require high powered lasers, which is beneficial for instance in integrated photonic circuits. We also show a new nonlinear compression regime and soliton shaping dynamic only seen in sign-alternating dispersion waveguides. Through an example SiN-based integrated waveguide, we show that the dynamic enables the attainment of compression to two optical cycles at a pulse energy of 100 pJ which surpasses the compression achieved using similar parameters for a current state-of-the-art SiN system.

• H. Zia, “Nonlinear Pulse Compression to Shorter Durations than the Fundamental Soliton Limitation”, OSA Advanced Photonics. Invited talk at Fiber Modelling and Fabrication Technical Group Poster Session.
• H. Zia, “Nonlinear Pulse Compression to Shorter Durations than the Fundamental Soliton Limitation”, OSA Advanced Photonics. Joint Poster Session.
• H. Zia, “New Nonlinear Propagation Dynamics in Structured Dispersion Systems”, Global Summit and Expo on Laser Optics and Photonics (GSELOP2021), Invited talk.
• H. Zia, Enhanced Pulse Compression within Sign-Alternating Dispersion Waveguides, OSA High Brightness Congress (2020). Talk
• H. Zia, N. M. Luepken, T. Hellwig, C. Fallnich, K-J. Boller, ” Sign-Alternating Dispersion Patterning for Supercontinuum Generation,” in Conference on Lasers and Electro-Optics Europe-EQEC (2019). Talk.
• H. Zia, N. M. Luepken, T. Hellwig, C. Fallnich, K-J. Boller, “Overcoming Spectral Stagnation in Supercontinuum Generation,” in Conference on Lasers and Electro-Optics, OSA Technical Digest (Optical Society of America, 2019), paper FF2D.5. Talk.
• H. Zia, N. M. Luepken, T. Hellwig, C. Fallnich, K-J. Boller, [email protected] 2019, poster presentation.