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The image depicts the generation of high-dimensional orbital angular momentum (OAM) comb by an azimuthal binary phase. The proposed azimuthal phase is 0-&pi; binarized, with a series of azimuthal transition lines dividing the phase value 0 and &pi;. Such phase element can transform a Gaussian beam into an OAM multiplexed beam consisting of multiple equally spaced OAM channels with identical power&minus;namely, an OAM comb.

Periodic poling of resonant lithium niobate metasurfaces modifies their nonlinearity and enables tailoring the diffraction pattern of second harmonic generated by the metasurface. It adds another degree of freedom for designing nonlinear metasurfaces.

The small size and rich functions of metasurfaces have great potential for the development of new optical devices. The research group theoretically proved that the metasurface can realize the complete decoupling of the near-field and far-field functions of the same polarization at two working wavelengths. While the near-field encodes intensity patterns, the far-field functions can be holographic, focusing, and beam deflecting. The cover image shows that when a metasurface is illuminated by the light at 1064 nm and 1550 nm, the near-field intensity distribution displays the numbers 1064 and 1550, and the holographic pattern shows the emblem of Nanjing University and its landmark building North Building.

Helical laser beams, due to their unique field structure, are ideal optical drivers for producing monoenergetic, pellet-like electron bunches. In contrast to regular laser beams, their field structure close to the axis of the beam is dominated by longitudinal electric and magnetic fields. The bunches are generated as a result of two synergetic effects that take place when such a beam is reflected off a mirror: the longitudinal electric field accelerates electrons after extracting them from the mirror surface; while the magnetic field confines them into the central region, allowing for acceleration within the laser over a long duration.

The image on the cover for Advanced Photonics Volume 5 Issue 1 illustrates a torus-knot configuration of a toroidal layer in the Hopf fibration and its vectorial properties of a photonic hopfion, which is controllably transported in free space. The image is based on original research presented in the article by Yijie Shen, Bingshi Yu, Haijun Wu, Chunyu Li, Zhihan Zhu, and Anatoly V. Zayats, “Topological transformation and free-space transport of photonic hopfions,” Adv. Photonics 5(1), 015001 (2023), doi: 10.1117/1.AP.5.1.015001.

Editors' Picks
Bound states in the continuum (BICs) are nonradiative states embedded in the spectra of the radiation continuum. The mechanism of BICs provides efficient ways to engineer the quality factor (Q factor) of resonant modes. Recent demonstrations reveal that metallic metasurfaces can support high-Q plasmonic quasi-BICs offering unprecedented opportunities to achieve giant optical field enhancement. This allows for many applications requiring strong light-matter interaction, such as laser generation, Bose-Einstein condensation, and nonlinear enhancement.
Photonics Research
• Mar. 16, 2023
• Vol. 11, Issue 2 (2023)
Community-Publication
A new way to create high-energy ions could speed up their applications in treating cancer and probing the fundamental nature of matter.
High Power Laser Science and Engineering
• Mar. 14, 2023
• Vol. , Issue (2023)
HPL Highlights
Light with spiral phases, known as optical vortex, can carry orbital angular momentum (OAM), and is widely applied in microscale matter manipulation, microscopy, optical communication, intense laser interaction with materials, and so on. With the development of ultrashort and ultra-high power lasers, whose vortex versions have drawn significant attention. However, the existing high-energy-flux mode-converter, large size reflective phase-plate installed at the end of the laser, suffers from expensive cost, low spatial resolution, limited damage threshold, and is disturbed by topological charge dispersion which can degrade the vortex quality. Broadband mode-converter, e.g. Q-plate (a half waveplate with the optical axis rotating with azimuth), can realize broadband mode conversion but the energy flux is limited by its small manufacturable size.
High Power Laser Science and Engineering
• Mar. 14, 2023
• Vol. 10, Issue 5 (2023)
HPL Highlights
Laser-induced particle acceleration attracts the interest of the scientific community due to its numerous potential applications in inertial confinement fusion, medical applications such as hadron therapy, as well as due to the fundamental physics involved. An experimental team from the Institute of Plasma Physics & Lasers (IPPL) of the Hellenic Mediterranean University – HMU focuses on the experimental production of the optimal target profiles to be irradiated by the ZEUS laser to deliver accelerated protons having the maximum energy and population possible.
High Power Laser Science and Engineering
• Mar. 14, 2023
• Vol. 10, Issue 5 (2023)
HPL Highlights
Laser damage to mirror coatings caused by nodule defects is one of the bottlenecks limiting further increases in output power of high-power laser facilities. Nodule defects grow from particles on the substrate surface or particles generated during the coating deposition process into inverted cones with domed tops, resulting in unwanted localized electric (E)-field enhancement and coating layer discontinuities. The micro-lens model and angular-dependent transmission model suggest that localized E-field enhancement can lead to nodule ejection under laser irradiation. Due to the diversity of seed sources, nodules are unavoidable in laser coatings. Traditionally, laser conditioning and nodule planarization methods are used to reduce the adverse effects of nodule defects. However, laser conditioning produces plasma scalds and nodule-ejected pits; nodule planarization is limited to ion-beam sputtering deposition, not e-beam evaporation – a technique especially suitable for large, high-power laser optics.
High Power Laser Science and Engineering
• Mar. 14, 2023
• Vol. 10, Issue 5 (2023)
Scattered light imaging beyond the memory effect using the dynamic properties of thick turbid media

Scattered light imaging through complex turbid media has significant applications in biomedical and optical research. For the past decade, various approac

Scattered light imaging through complex turbid media has significant applications in biomedical and optical research. For the past decade, various approaches have been proposed for rapidly reconstructing full-color, depth-extended images by introducing point spread functions (PSFs). However, because most of these methods consider memory effects (MEs), the PSFs have angular shift invariance over certain ranges of angles. This assumption is valid for only thin turbid media and hinders broader applications of these technologies in thick media. Furthermore, the time-variant characteristics of scattering media determine that the PSF acquisition and image reconstruction times must be less than the speckle decorrelation time, which is usually difficult to achieve. We demonstrate that image reconstruction methods can be applied to time-variant thick turbid media. Using the time-variant characteristics, the PSFs in dynamic turbid media within certain time intervals are recorded, and ergodic scattering regimes are achieved and combined as ensemble point spread functions (ePSFs). The ePSF traverses shift-invariant regions in the turbid media and retrieves objects beyond the ME. Furthermore, our theory and experimental results verify that our approach is applicable to thick turbid media with thickness of 1 cm at visible incident wavelengths.show less

• Mar.22，2023
• Advanced Photonics Nexus,Vol. 2, Issue 2
• 026010 (2023)
Y3Al5O12:Ce3+ fluorescent ceramic for optical data storage

A kind of optical data storage medium based on electron-trapping materials, Y3Al5O12:Ce3+ fluorescent ceramic, was developed by vacuum sintering technolog

A kind of optical data storage medium based on electron-trapping materials, $Y3Al5O12:Ce3+$ fluorescent ceramic, was developed by vacuum sintering technology. The medium shows sufficiently deep traps (1.67 and 0.77 eV). The properties of trap levels were researched by thermoluminescence curves, and the optical storage mechanism based on $Ce3+$ ion doping was proposed. More importantly, the data can be written-in by 254 nm UV light, and readout by heating (300°C). This work expands the application fields of fluorescent ceramics, and it is expected to promote the development of electron-trapping materials.show less

• Mar.22，2023
• Chinese Optics Letters,Vol. 21, Issue 4
• 041602 (2023)
Watt-level laser operation of Pr3+:YLF at 696 and 698 nm

We report continuous-wave deep red lasers at 696.6 and 698.6 nm in a Pr3+:YLF crystal pumped by an InGaN laser diode. A Lyot filter was inserted into the

We report continuous-wave deep red lasers at 696.6 and 698.6 nm in a $Pr3+:YLF$ crystal pumped by an InGaN laser diode. A Lyot filter was inserted into the cavity as a birefringent filter to select wavelength; the lasers at 696.6 and 698.6 nm were obtained with a maximum output power of 1.36 and 3.11 W, separately. To the best of our knowledge, the output powers of these two lasers are the highest to date, and this is the first scaling of the output power of the $Pr3+:YLF$ laser to the watt level at around 696 nm. In addition, the corresponding theoretical analysis and simulation were carried out to explain the experimental phenomena.show less

• Mar.22，2023
• Chinese Optics Letters,Vol. 21, Issue 4
• 041404 (2023)
Highly sensitive torsion sensor based on Mach–Zehnder interference in helical seven-core fiber taper

We propose a high-sensitivity bidirectional torsion sensor using a helical seven-core fiber taper embedded in multimode fiber (MHSTM). Sensors with differ

We propose a high-sensitivity bidirectional torsion sensor using a helical seven-core fiber taper embedded in multimode fiber (MHSTM). Sensors with different taper waists and helical pitches are fabricated, and their transmission spectra are obtained and analyzed. The waist and length of the sandwiched seven-core fiber are finally determined to be 68 µm and 3 mm, respectively. The experimental results show that the clockwise and counterclockwise torsion sensitivities of the proposed sensor are 2.253 nm/(rad/m) and -1.123 nm/(rad/m), respectively. When tapered waist diameter reduces to 48 µm, a superior torsion sensitivity of 5.391 nm/(rad/m) in the range of 0–4.24 nm/(rad/m) is obtained, which is 46 times as large as the traditional helical seven-core fiber structure. In addition, the MHSTM structure is also relatively stable to temperature variations.show less

• Mar.22，2023
• Chinese Optics Letters,Vol. 21, Issue 4
• 041205 (2023)

We demonstrate an all-polarization-maintaining (PM) passively mode-locked Yb3+-doped fiber laser (YDFL) with a fundamental repetition rate of 1.3 GHz. The optical spectra of linearly po

We demonstrate an all-polarization-maintaining (PM) passively mode-locked Yb3+-doped fiber laser (YDFL) with a fundamental repetition rate of 1.3 GHz. The optical spectra of linearly polarized soliton exhibit different shapes by rotating the fast axis of the fiber optical pigtail of a dispersive dielectric mirror. The oscillator provides a series of laser performance, such as a threshold pump power for continuous wave laser oscillation of 3.1 mW, an optical-to-optical efficiency for mode-locking of 29%, and an integrated relative intensity noise of 0.08%. To the best of our knowledge, this is the first report of >1 GHz ultrafast all-fiber YDFL with PM architecture.show less

• Mar.22，2023
• Chinese Optics Letters,Vol. 21, Issue 6
• (2023)

An optical scrambler using a whispering-gallery-mode micro bottle cavity is proposed to scramble a complex optical signal to generate an uncorrelated output. We experimentally demonstra

An optical scrambler using a whispering-gallery-mode micro bottle cavity is proposed to scramble a complex optical signal to generate an uncorrelated output. We experimentally demonstrated this micro-cavity scrambler by using a chaotic laser light as incident signal and studied the influences of the coupling state. Experiments achieved a fully scrambling with a low cross correlation of 0.028 between the output and the input. Results indicate that the scrambling effect originates from the interference among numerous WGMs in the bottle cavity. It is believed that the micro bottle cavity having an efficient scrambling function can become a promising candidate for encryption. show less

• Mar.22，2023
• Chinese Optics Letters,Vol. 21, Issue 6
• (2023)

The high peak-power of picosecond pulses produced by a self-mode-locked semiconductor disk laser can effectively improve the efficiency of nonlinear frequency conversion. This paper pre

The high peak-power of picosecond pulses produced by a self-mode-locked semiconductor disk laser can effectively improve the efficiency of nonlinear frequency conversion. This paper presents the intra-cavity frequency-tripling in a self-mode-locked semiconductor disk laser, and picosecond pulses train at 327 nm wavelength is achieved. The pulse repetition rate is 0.49 GHz and the pulse width is 5.0 ps. The obtained maximum ultraviolet output power under mode-locking is 30.5 mW, and the corresponding conversion efficiency is obviously larger than that of continuous-wave operation. This ultraviolet picosecond pulses have high spatial and temporal resolution, and can be applied in some emerging fields.show less

• Mar.22，2023
• Chinese Optics Letters,Vol. 21, Issue 5
• (2023)

Light plays the central role in many applications. The key to unlocking its versatility lies in shaping it into the most appropriate form for the task at hand. Specifically tailored ref

Light plays the central role in many applications. The key to unlocking its versatility lies in shaping it into the most appropriate form for the task at hand. Specifically tailored refractive index modifications, directly manufactured inside glass using a short pulsed laser, enable an almost arbitrary control of the light flow. However, the stringent requirements for quantitative knowledge of these modifications, as well as for fabrication precision, have so far prevented the fabrication of light-efficient aperiodic photonic volume elements (APVEs). Here we present a powerful approach to the design and manufacturing of light-efficient APVEs. We optimize application-specific 3D arrangements of hundred thousands of microscopic voxels and manufacture them using femtosecond direct laser writing inside millimeter-sized glass volumes. We experimentally achieve unprecedented diffraction efficiencies up to 80\%, which is enabled by precise voxel characterization and adaptive optics during fabrication. We demonstrate APVEs with various functionalities, including a spatial mode converter and combined intensity shaping and wavelength-multiplexing. Our elements can be freely designed and are efficient, compact and robust. Our approach is not limited to borosilicate glass, but is potentially extendable to other substrates, including birefringent and nonlinear materials, giving a preview of even broader functionalities including polarization modulation and dynamic elements.show less

• Mar.22，2023