Generation of high-energy narrowband 2.05 μm pulses for seeding a Ho:YLF laser


Potential applications in attosecond science and high harmonic generation are among the driving forces propagating the development of high-energy and few-cycle mid-infrared lasers. Lasers of such attributes have been a topic of interest in the ultrafast laser community. Currently, great progress has been made on the generation of high energy short-pulse mid-infrared laser sources above 3 μm. However, the spectral bandwidth has not reached one octave, which limits the pulse duration to multicycle. In a previous study, a scheme for generation of terawatt sub-cycle 4–12 μm pulses through optical parametric chirped pulse amplification in ZGeP2 pumped by an Ho:YLF laser was designed. Due to the combined use of a pump from an Ho:YLF laser and a signal from a Ti:sapphire laser, complications in the synchronization of the two laser sources emerged. To this note, a high-energy source deriving from the Ti:sapphire laser is needed to seed the Ho:YLF laser.

Researchers led by Professor Zenghu Chang from the Institute for the Frontier of Attosecond Science and Technology at University of Central Florida designed and experimentally demonstrated the efficient generation of narrowband 2.05 μm pulses pumped with a broadband Ti:sapphire laser via dual-chirped optical parametric amplification (DC-OPA). They also successfully achieved a 82 μJ narrowband 2.05 μm pulses from a 1 mJ Ti:sapphire laser pulse. Their work is now published in the research journal, Photonics Research.

Their experiments and techniques employed entailed the use of a Ti:sapphire laser pulse energy of 1 mJ  for the DC-OPA, which was split into two portions. A certain percentage of the 1 mJ beam was made to pass through a neutral density filter and an iris diaphragm and was then focused onto a 3 mm thick sapphire plate to generate a stable single-filament continuum, which was the signal for seeding the DC-OPA. The signal was positively chirped by passing through a  20.6 mm thick ZnSe plate. The remaining percentage of the 1 mJ Ti:sapphire laser was the pump, which passed through a 45 mm thick SF57 plate with the same positive dispersion. A telescope was utilized to change the pump beam size on the BBO crystal. Eventually, a silicon plate was employed to separate the signal and idler beams from the pump beam.

The research team observed that the idler center wavelength could be easily tuned around 2.05 μm in order to accommodate the gain spectrum of any Ho:YLF laser amplifier by altering the delay between the signal and the pump. In addition, the researchers noted that the bandwidth could also be tuned by varying the input chirp of pump and signal.

Yanchun Yin and colleagues in their study presented novel design of a DC-OPA that utilizes BBO crystal as the nonlinear media for generating narrowband pulses, which are pumped by broadband Ti:sapphire laser pulses. Yanchun said, “when the broadband pump and the broadband signal have an equal amount of chirp, the frequency difference of all phase-matched pump-signal pairs is a constant and thus generates a single-wavelength idler. Based on this principle, you can actually generate nearly transform-limited narrowband pulses from high-chirped broadband pulses. You need to find the right crystal to do this.” From the experimental procedure undertaken, it has been proven that 82 μJ narrowband 2.05 μm pulses can be generated with 1 mJ pump in a BBO crystal. Altogether, the high-energy narrowband 2.05 μm pulse can be an ideal source for seeding a Ho:YLF multipass amplifier due to the ease of synchronization that it can help achieve when using a Ti:sapphire laser and a Ho:YLF laser for the development of mid-infrared laser pulses.

high-energy narrowband 2.05um pulses for seeding a Ho-YLF-laser-Advances in Engineering

About the author

Professor Zenghu Chang 

Zenghu Chang is a University Trustee Chair, Pegasus and  Distinguished Professor of Physics and Optics at the University of Central Florida, where he directs the Institute for the Frontier of Attosecond Science and Technology. He is a fellow of the American Physical Society and Optical Society of America.

Chang graduated from Xi’an Jiaotong University in 1982. He then earned a doctorate at the Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, in 1988. From 1991 to 1993, Chang visited the Rutherford Appleton Laboratory sponsored by the Royal Society fellowship. He worked at the University of Michigan after 1996. Then joined the physics faculty at Kansas State University in 2001, where he was later promoted to the Ernest & Lillian Chapin Professor.

Dr. Chang has published 180 papers in the field of ultrafast high power lasers, ultrafast XUV/X-ray science and strong field AMO physics. His notable contributions include inventing the Double Optical Gating for the generation of single isolated attosecond pulses. He is the author of the book “Fundamentals of Attosecond Optics.” His group generated the shortest XUV laser pulse (67 as) in 2013, and then generated the shortest soft X-ray laser pulse (53 as) at the carbon K-edge in 2017.

About the author

 Dr. Yanchun Yin

Dr. Yanchun Yin is an expert in development of state-of-art ultrafast lasers. He is currently a research scientist in CROEL and Physics at the University of Central Florida. He received his Ph.D degree focusing on ultrafast lasers and optics from The Pennsylvania State University in 2014 and his B.S. in Applied Physics in 2007 from Shandong University, China. Since then he has been working in Institute for the Frontier of Attosecond Science and Technology directed by Dr. Chang.

He has many years of research experience in ultrafast lasers and optics with expertise in developing (both modeling and building) high-energy and few-cycle IR and MIR laser pulses through optical parametric amplification (OPA), optical parametric chirped-pulse amplification (OPCPA), and chirped pulse amplification (CPA). In addition, he has expertise in high harmonic generation in both gas and solids, and attoseond pulse generation in the soft X-ray region.

His achievements include but not limited to development of highest-efficiency and highest-energy two-cycle, CEP-stable laser at 1.7 µm via OPCPA, generation of a 6.8 µJ laser pulse spanning from 1.8 to 4.2 µm from cascaded second-order nonlinear processes in a single crystal, and design of a mJ-level two-cycle laser pulse at 3.2 µm via dual-chirped optical parametric amplification (DC-OPA).


Yanchun Yin, Xiaoming Ren, Yang Wang, Fengjiang Zhuang, Jie Li, Zenghu Chang. Generation of high-energy narrowband 2.05 μm pulses for seeding a Ho:YLF laser. Volume 6, No. 1 / January 2018 / Photonics Research.


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