Laser processing plays a key role in treating a lot of materials. The mechanism of laser stealth dicing (SD) is based on irradiation of a laser beam which is focused inside the brittle material. The laser beam scans along the predetermined path, so that the characteristics of the interior brittle material can be changed, the stress layer can be therefore formed. Finally, an external force is applied to separate the brittle material. Since only the limited interior region of a wafer is processed by the laser irradiation, the damages and debris contaminants can be avoided during the SD process. SD has the advantages of a high speed for thinner wafers without any chipping, the smooth section without dust and slag, and completely dry process, which has been widely used in large scale integrated circuits and microelectronic manufacturing systems. However, further studies on the simulation analyze and parameter optimization have kept to be rear for SD so far. In this study, an approach named as constrained interpolation profile (CIP) was adopted, which has the advantages of compactness, stability, and low dissipation in computational fluid dynamics compared with other simulation procedures. We have finished a theoretical simulation to obtain the physical features of the temperature, pressure, density of the silicon substrate at different focal depth where a nanosecond pulsed laser is irradiated, then we found a suitable focal depth with a good dicing quality by analyzing these physical features.
We report the experimental observation of the squeezing effect in a graphene mechanical resonator due to an optical actuation force. We fabricate a circular suspended graphene mechanical resonator and measure two quadrature components of the mechanical mode via a phase-locked demodulation technique. By analyzing the correlated distribution of the two components, we find a squeezing effect when increasing the actuation power. We also observe singularity phenomena right at the cut-off frequency, which might be related to the nonlinear effect. Further study is needed to fully understand these phenomena. Our results might find new applications in the fields of sensing and mechanical information processing.
We present an optically assisted frequency modulation (FM) demodulation method to characterize the resonance mode of a graphene resonator. The intensity of a laser at 795 nm is FM demodulated to actuate the graphene resonator, where the carrier frequency is approximately around the resonant frequency of the resonator and the FM deviation is set by the reference signal from the lock-in amplifier. A continuous laser at 633 nm is directed in the sample to perform the optical interferometry technique and the resonance mode of the graphene resonator is extracted through the lock-in amplifier. In this way, resonance modes at high frequencies much larger than the bandwidth of the lock-in amplifier could be detected within a high accuracy. In our configuration, we have obtained the graphene resonance mode at frequencies around 10 MHz with a 100 kHz bandwidth lock-in amplifier.
Laser processing plays a key role in treating a lot of materials. The visible nanosecond laser processing based on a tripartite-interaction system has been proved to be an effective method of processing materials with high optical transparency, which has the advantages of low cost, high efficiency, and simplicity over the direct processing by using a femtosecond laser. However, further studies on the theoretical mechanism and parameter optimization keep to be rear for the hybrid tripartite-interaction laser processing. In this study, we have carried out the confirmatory experiment and numerical simulation of laser processing with a tripartite-interaction system, which includes a visible nanosecond laser (19 ns@532 nm), a piece of transparent glass, and a copper foil. The experiment indicates that drilled holes can be obtained on the glass sheets by using the visible nanosecond laser. The numerical results, which have been obtained by an approach named as constrained interpolation profile, reveal that the processing mechanism is based on the heat conduction, generation of stress and ablation between the glass and the copper foil. Our results could to be useful for the development of visible nanosecond laser processing in industrial applications.
It has always been difficult to process a metal film with high reflectivity in the field of manufacture, industry, medicine, and military, etc. Since much of the laser energy can be reflected especially when the reflectance of the target film surface is high, it is hard to process such a metallic film by laser radiation as the energy absorbed by the film material is very little. In this paper, we used a nanosecond pulsed laser to scribe some patterns on a smooth titanium (Ti) film, and investigated the surface morphology of a Ti film ablated by different laser spot sizes and laser energy. In our experiments, it has been found that the Ti film can be efficiently processed although the surface reflectance of the Ti film is about 57% at the wavelength of 532 nm. We also see that the processing range of the Ti film will decrease when the diameter of a laser beam increases. The experimental results show that the ablated status of the surface of a Ti film for a just-focus beam is much better than that for a defocus beam under the same laser power. Furthermore, the higher the laser power, the larger the processed area. By using the optimal parameters we obtained, we also produced some hole matrices and line patterns on a glass-based Ti film by employing a short pulsed laser. The processed samples were observed with a reflecting microscope and a transmitting microscope, respectively. Our research results can play an important role in the selection of laser parameters for laser processing of some materials with a high reflectivity.
In this work, we propose and demonstrate the frequency-bin entangled two-photon state via cascaded second harmonic generation and spontaneous parametric down conversion (SHG-SPDC) processes in a single piece of PPLN waveguide. Our scheme is based on all fiber-pigtailed components at 1.5 μm telecom band. Two frequency-bins at 1531.34 nm and 1548.91 nm with bandwidth of 1.04 nm are prepared to be entangled. The frequency entanglement property of our generated two-photon states is measured by spatial two-photon quantum beating. A two-photon beating curve with a visibility of 87.92±0.47% is obtained, showing a good property of frequency-bin entanglement.
In this study, we propose and experimentally demonstrate a picosecond pulse laser at 850 nm. To generate picosecond laser pulse, we operate a vertical cavity surface emitting laser under a gain-switched pulsed mode, which is realized by driving it with our home-made drive circuit based on field programmable gate array and radio frequency devices. The obtained laser pulses are with the pulse width of less than 675 ps, and with repetition rate from single shot to megahertz. On the other hand, based on our gain-switched pulsed laser, we design and realize a cost-effective optical time domain reflectometry prototype equipment with photon counting technology for monitoring the healthy condition of aeronautical fiber. Our prototype equipment achieves a spatial resolution of less than 9 cm, and a dynamic range of around 18 dB above the noise floor. Such prototype equipment has already been employed to monitor an optical cable with 32 fiber channels on plane.
Benefit from the recent nanotechnology process, people can integrate different nanostructures on a
single chip. Particularly, quantum dots (QD), which behave as artificial atoms, have been shown to
couple with a superconducting resonator, indicating that quantum-dot based quantum chip has a highly
scalable possibility. Here we show a quantum chip architecture by combining graphene quantum dots
and superconducting resonators together. A double quantum dot (DQD) and a microwave hybrid
system can be described by the Jaynes-Cummings model, while a multi-quantum-dots system is
conformed to the Tavis-Cummings model. These simple quantum optics models are experimentally
realized in our device, providing a compelling platform for both graphene study and potential
applications.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.