English

Tailoring 'hollow' hydrogen molecule generation with two-color, bicircularly polarized laser pulses

978
2023-09-16 14:21:25
See translation

Rydberg atoms and molecules are characterized by having one or more electrons in highly excited bound states. Such atoms and molecules are said to be in “Rydberg states” and are also called “hollow” atoms and molecules. Rydberg states are useful for studying various phenomena arising in intense light–matter interaction that involve electronic excitation with an intense laser pulse via optical processes like “multiphoton resonant excitation” and “frustrated tunneling ionization.”

In multiphoton resonant excitation, atoms or molecules are excited to Rydberg states through the absorption of multiple photons (units of electromagnetic radiation). In contrast, frustrated tunneling ionization-induced Rydberg states result from an interaction between the electron and the intense electric field of the laser. Thus, both the laser photon and the laser field jointly contribute to the Rydberg state excitation (RSE) process. However, the extent of the individual contributions of these two effects has not been experimentally determined so far.

Now, in a study published in Advanced Photonics, a team of researchers led by Professor Jian Wu from East China Normal University has developed an experimental method to isolate the effects of each mechanism in RSE.

Their method involves exciting hydrogen molecules to Rydberg states by controlling the photon effect and field effect using a bicircular two-color (BCTC) laser field, a type of laser field that is generated by combining two circularly polarized laser beams with different frequencies. Using two laser beams enabled the researchers to adjust the energy of the photons that are used to excite the hydrogen atoms.

 Additionally, by changing the helicity of the BCTC field, they were able to switch the electron recapture processes on and off, manipulating the field effect. Thus, they were able to generate Rydberg states while varying the extent to which each effect contributed to the process. The researchers then determined the extent to which the field excitation and photon absorption processes contributed to RSE by comparing the Rydberg state yields for different polarizations and photon counts.

“By finely adjusting the relative field strength of the two colors, we could manipulate the waveform of the laser field and the number of photons participating in the RSE processes and, in turn, the relative contributions of the field and photon effects,” explains Hongcheng Ni, the co-corresponding author of the work.

In their experimental setup, the BCTC laser fields were generated using the combination of a fundamental wave (FW) laser pulse and a second harmonic (SH) pulse with twice the fundamental frequency. These pulses were combined using a dichromatic mirror to generate either counter- or co-rotating two-color laser fields. These pulses were then focused on a supersonic jet of hydrogen gas inside a reaction microscope to create Rydberg states of hydrogen molecules.

The researchers found that increasing the relative strength of the SH field (with photons twice as energetic as the FW field) led to an overall increasing yield of Rydberg states, indicating an important role of the photon effect. Additionally, switching the polarization of the BCTC field from co-rotating to counter-rotating also led to an increase in the Rydberg state yield. The researchers attributed this observation to the suppression of the field effect for co-rotating fields.

The experimental study provides important insights into RSE in an intense laser field with potential implications for a wide range of fields, including quantum physics, chemistry, and astrophysics. “Rydberg atoms and molecules have the potential to serve as building blocks for advanced technologies related to quantum information, quantum nonlinear optics, long-range many-body interactions, and precision measurements. In this regard, our study can offer a promising route for manipulating and optimizing the RSE yields under intense laser field excitations,” says Wenbin Zhang, the first author and co-corresponding author of the work.

The promises held by hollow atoms certainly don’t ring hollow!

Source: SPIE

Related Recommendations
  • Trumpf China 25 Years: From Model Factory to Global Strategic Fortress

    On March 14, 2000, Trumpf established its first company in China - Trumpf Metal Sheet Products Co., Ltd., headquartered in Taicang, 50 kilometers northwest of Shanghai. Nowadays, Taicang has become a global strategic stronghold for the company. 25 years ago, this production base was originally used to demonstrate sheet metal processing production for Chinese enterprises. In the seventh year afte...

    03-26
    See translation
  • Overview of ultrafast laser micro nano manufacturing technology: material processing, surface/interface control, and device manufacturing

    Researchers from Tsinghua University have summarized the research on ultrafast laser micro nano manufacturing technology, including material processing, surface/interface control, and device manufacturing. The relevant review titled "A Review of Ultrafast Laser Micro/Nano Fabric: Material Processing, Surface/Interface Control, and Device Fabric" was published in Nano Research.Ultra fast laser proc...

    2024-08-06
    See translation
  • Photon chips help drones fly unobstructed in weak signal areas

    With funding from the National Science Foundation of the United States, researchers at the University of Rochester are developing photonic chips that use quantum technology called "weak value amplification" to replace mechanical gyroscopes used in drones, enabling them to fly in areas where GPS signals are obstructed or unavailable.Using this quantum technology, scientists aim to provide the same ...

    2023-10-28
    See translation
  • Tiny yet Powerful: How Lasers on Chips Change the Game Rules of Photonics

    Chip level ultrafast mode-locked laser based on nanophotonic lithium niobate.Researchers have created a compact mode-locked laser integrated into a nanophotonic platform, capable of generating high-power and ultrafast optical pulses. The breakthrough in miniaturization of MLL technology can significantly expand the application of photonics.Innovation in mode-locked laser technologyTo improve the t...

    2023-12-27
    See translation
  • 国内自主研发首套碳化硅晶锭激光剥离设备投产

           近日,从江苏通用半导体有限公司传来消息,由该公司自主研发的国内首套的8英寸碳化硅晶锭激光全自动剥离设备正式交付碳化硅衬底生产领域头部企业广州南砂晶圆半导体技术有限公司,并投入生产。 图:8英寸SiC晶锭激光全自动剥离设备       该设备可实现6英寸和8英寸碳化硅晶锭的全自动分片,包含晶锭上料、晶锭研磨、激光切割、晶片分离和晶片收集,一举填补了国内碳化硅晶锭激光剥离设备领域研发、制造的市场空白,突破了国外的技术封锁,将极大地提升我国碳化硅芯片产业的自主化、产业化水平。       该设备年可剥离碳化硅衬底20000片,实现良率95%以上,与传统的线切割工艺相比,大幅降低了产品损耗,而设备售价仅仅是国外同类产品的1/3。       近年来,碳化硅功率器件在大功率半导体市场中所占的份额不断提高,并被广泛应用于新能源汽车、城市轨道交通、风力发电、高速移动、物联网等一系列领域...

    2024-08-26
    See translation