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