Spatiotemporal optical vortices (STOVs) are a type of light beams that carry transverse orbital angular momentum (T-OAM), enabling the generation and control of additional degrees of freedom. However, the currently generated STOV wavepackets, whether with a single STOV or multiple sub-STOVs, typically exhibit a single circular symmetric structure in the spatiotemporal plane, limiting their potential in many applications. To address this limitation, we theoretically propose and experimentally demonstrate polygonal spatiotemporal optical vortices wavepackets embedded with prescribed vortex structures. Within the structure, a prescribed number of sub-STOVs carrying T-OAM is set along a designed polygonal spatiotemporal trajectory. Using the spatiotemporal holographic shaping approach, we generate a polygonal perfect STOV wavepacket and use the combination of two polygonal perfect STOV wavepackets to form a polygonal STOV wavepacket with the prescribed vortex structure. Full control over multiple key properties of the polygonal STOV wavepackets such as the geometry, number of phase singularities, and spatiotemporal distribution of sub-STOVs is also achieved. This ability provides a way to customize STOV wavepackets with complex topological structures. These spatiotemporal wavepackets will facilitate applications such as optical communication, the study of complicated quantum systems, and multiple-target particle manipulation. (c) 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

The ability to precisely focus optical beams is crucial for numerous applications, including imaging. The slow intensity transitions of conventional Gaussian beams near the focal point limit their effectiveness in scenarios requiring sharp focusing. Ultrafast self-focusing of circular Airy beams has been reported in two dimensions. Here we demonstrate this capability for spherical Airy wavepackets, a three-dimensional light field with an Airy function distribution in the radial direction. We sculpt spherical Airy wavepackets to exhibit ultrafast self-focusing with a substantially reduced depth of focus, compared with both conventional Gaussian beams and circular Airy beams. Our measurements confirm the wavepacket's nonlinear intensity increase and tight spatiotemporal confinement. The superior focusing dynamics of spherical Airy wavepackets are broadly applicable to high-resolution imaging, nonlinear optics and optical trapping. Overcoming current limitations from pixelated modulation devices, such as spatial light modulators, could further enhance focusing performance, paving the way for advanced applications in biomedical imaging, laser processing and ultrafast optics.

Recently,spatiotemporal optical vortices(STOVs) with transverse orbital angular momentum have emerged as a significant research topic.While various STOV fields have been explored,they often suffer from a critical limitation:the spatial and temporal dimensions of the STOV wavepacket are strongly correlated with the topological charge.This dependence hinders the simultaneous achievement of high spatial accuracy and high topological charge.To address this limitation,we theoretically and experimentally investigate a new class of STOV wavepackets generated through the spatiotemporal Fourier transform of polychromatic Bessel-Gaussian beams,which we term as perfect spatiotemporal optical vortices.Unlike conventional STOVs,perfect STOVs exhibit spatial and temporal diameters that are independent of the topological charge.Furthermore,we demonstrate the generation of spatiotemporal optical vortex lattices by colliding perfect STOV wavepackets,enabling flexible manipulation of the number and sign of sub-vortices.

The ability to precisely focus optical beams is crucial for numerous applications, yet conventional Gaussian beams exhibit slow intensity transitions near the focal point, limiting their effectiveness in scenarios requiring sharp focusing. In this work, the spherical Airy wavepacket, a three dimensional light field with an Airy function distribution in the radial direction in the full space time domain, is introduced and experimentally demonstrated. Leveraging the recently developed spatiotemporal hologram technique and an exponential polar coordinate transformation, spherical Airy wavepacket is sculpted to exhibit ultrafast autofocusing with a dramatically reduced depth of focus compared to conventional Gaussian beams and circular Airy beams. Experimental measurements confirm its nonlinear intensity surge and tight spatiotemporal confinement.

Airy beams, celebrated for their self-acceleration, diffraction-free propagation, and self-healing properties, have garnered significant interest in optics and photonics, with applications spanning ultrafast optics, laser processing, nonlinear optics, and optical communications. Recent research primarily aims at independent control of Airy beams in both spatial and spatiotemporal domains. In a pioneering approach, we have successfully generated and controlled a spatiotemporal coupled (STc) Airy-Airy wavepacket, achieving its rotation while preserving vertical distribution in the spatiotemporal domain. Furthermore, we have investigated the self-acceleration and self-healing properties of the STc Airy-Airy wavepacket in this domain, noting that its dynamically adjustable rotation and spatiotemporal coupling capability provide a novel strategy for managing ultrafast lasers, with potential advancements in optical micromanipulation and time-domain coding communication.

Airy beams, celebrated for their self-acceleration, diffraction-free propagation, and self-healing properties, have garnered significant interest in optics and photonics, with applications spanning ultrafast optics, laser processing, nonlinear optics, and optical communications. Recent research primarily aims at independent control of Airy beams in both spatial and spatiotemporal domains. In a pioneering approach, we have successfully generated and controlled a spatiotemporal coupled (STc) Airy-Airy wavepacket, achieving its rotation while preserving vertical distribution in the spatiotemporal domain. Furthermore, we have investigated the self-acceleration and self-healing properties of the STc Airy-Airy wavepacket in this domain, noting that its dynamically adjustable rotation and spatiotemporal coupling capability provide a strategy for managing ultrafast lasers, with potential advancements in optical micromanipulation and time-domain coding communication.

Airy waves, known for their non-diffracting and self-accelerating properties, have been extensively studied in spatial and temporal domains, but their spatiotemporal (ST) counterparts remain largely unexplored. We report the first experimental realization of a spatiotemporal Airy rings wavepacket, which exhibits an Airy function distribution in the radial dimension of the ST domain. The wavepacket demonstrates abrupt autofocusing under the combined effects of diffraction and dispersion, achieving a 110 um spatial and 320 fs temporal focus with a sharp intensity contrast along the propagation direction - ideal for nonlinear microscopy and multiphoton 3D printing. Notably, the wavepacket retains its autofocusing capability even after spatial obstruction, showcasing robust self-healing. Furthermore, by embedding a vortex phase, we create an ST-Airy vortex wavepacket that confines transverse orbital angular momentum (t-OAM) within a compact ST volume, enabling new avenues for studying light-matter interactions with t-OAM. Our findings advance the fundamental understanding of ST Airy waves and highlight their potential for transformative applications in ultrafast optics, structured light, and precision laser processing.

We report the experimental observation of a three-dimensional abruptly autofocusing effect by synthesizing a radially distributed Airy beam with two counter-propagating Airy pulses in time. As the wave packet propagates in a dispersive medium, the radially distributed Airy beam converges inward to the center point. Two Airy pulses counter-propagate toward each other to merge to form a high-peak-power pulse. As a result, high intensity emerges abruptly as the wave packet achieves three-dimensional focusing. This autofocusing effect is believed to have potential applications such as material modification, plasma physics, and nanoparticle manipulations.

Spatiotemporal optical vortices with arbitrary tilt angles can be generated by adjusting spatial chirp and beam size at a phase modulation plane in a pulse shaper setup. A grating pair setup is proposed to generate variable spatial chirp independent of the beam profile. The initial dispersion of the pulse allows for the independent control of the vortex orientation. By adjusting the beam size, spatial chirp, and initial dispersion, arbitrary vortex orientation across all the possible angles can be achieved. The ability to achieve arbitrary vortex orientations at long propagation distances could offer significant advantages for long-distance communication applications.

A spectral filter utilizing dispersive prisms and an optical fiber collimator is presented as an attractive alternative to diffraction grating-based spectral filters. A simplified analytical expression for this prism-based spectral filter is derived. A spectral filter constructed using SF11 flint glass prisms demonstrates Gaussian spectral filter profiles with bandwidths of 8 nm and 4 nm, closely matching with theoretical predictions. Using these filters, we demonstrate two types of mode-locking regimes: a dissipative soliton (DS) pulse and a self-similar (SS) pulse. The dissipative soliton pulses deliver 3.3 nJ with dechirped pulse durations of 206 fs, while the self-similar pulses deliver 2.1 nJ with durations of 120 fs. The results demonstrate that the prism-based filters are well-suited for ultrafast mode-locked fiber lasers.

The transverse orbital angular momentum (OAM) of spatiotemporal optical vortices (STOVs) has been a topic of active debate in recent years. Previous studies, relying on narrowband and paraxial approximations, resulted in unprecedented conclusions. Some researchers have proposed that electromagnetic waves require a modified definition of OAM to ensure conservation. In this work, we demonstrate that the transverse OAM of STOVs is highly sensitive to these commonly adopted approximations. Using the standard definition of OAM for electromagnetic waves, we demonstrate that the total transverse OAM is conserved during propagation once the narrowband and paraxial assumptions are removed.

Optical vortices carrying orbital angular momentum offer additional degrees of freedom. According to the orientation of orbital angular momentum, optical vortices can be classified into spatial optical vortex beam carrying longitudinalorbital angular momentum and spatiotemporal optical vortices carrying transverse orbital angular momentum. As an emerging subset of optical vortices, polygonal optical vortices provide a unique platform for a wide range of frontier applications by introducing a new degree of freedom in the form of a customizable intensity structure. In the spatial domain, polygonal spatial optical vortex beam carrying longitudinal orbital angular momentum have already demonstrated great potential in optical manipulation and two-photon lithography. However, polygonal spatiotemporal optical vortex wavepackets contain multiple sub spatiotemporal optical vortices carrying transverse orbital angular momentum remains unrealized to date. In this work, we theoretically propose and experimentally demonstrate polygonal spatiotemporal optical vortices wavepackets embedded with prescribed vortex structures. Within the structure, a prescribed number of sub spatiotemporal optical vortices carrying transverse orbital angular momentum is set along a designed polygonal spatiotemporal trajectory. Using the spatiotemporal holographic shaping approach, we generate polygonal perfect spatiotemporal optical vortex wavepacket and use the combination of multiple polygonal perfect spatiotemporal optical vortex wavepacket to form polygonal spatiotemporal optical vortex wavepacket with the prescribed vortex structure. A full control over multiple key properties of the polygonal spatiotemporal optical vortex wavepackets such as the geometry, number of phase singularities, and spatiotemporal distribution of sub spatiotemporal optical vortices is also achieved.

Reconnections of spatiotemporal optical vortices have been shown to occur between line vortices. Here, we show that reconnections also occur between spatiotemporal loop vortices in optical waves. As optical loop vortices propagate in a media with spatial diffraction and material group velocity dispersion, unique reconnections occur. The birth and death of loops can occur, with certain loop vortices emerging from or collapsing to a single point while interacting with others. As certain parameters are varied in the model, complex arrangements of loops form in space-time from simple initial fields.

Photonic quantum emulator utilizes photons to emulate the quantum physical behavior of a complex quantum system. Recent study in spatiotemporal optics has enriched the toolbox for designing and manipulating complex spatiotemporal optical wavepackets, bringing new opportunities in building such quantum emulators. In this work, we demonstrate a new type of photonic quantum emulator enabled by spatiotemporal localized wavepackets with spherical harmonic symmetry. The spatiotemporal field distribution of these wavepackets has the same distributions of the wavefunction solutions to the potential-free Schrödinger equation with two controllable quantum numbers. A series of such localized wavepackets are experimentally generated with their localized feature verified. These localized wavepackets can propagate invariantly in space–time like particles, forming a new type of photonic quantum emulator that may provide new insight in studying quantum physics and open up new applications in studying light-matter interactions and quantum optics.

We present a theoretical study of a spectral filter, which consists of a diffraction grating, a coupling lens, and an optical fiber. As the diffracted beam is highly dispersed spatially, coupling into an optical fiber naturally creates a Gaussian spectral filtering effect. Using ray transfer matrices, we derive simple equations to calculate the spectral filter bandwidth and the group velocity dispersion. This study offers insights for designing fiber-based spectral filters, particularly for mode-locked fiber lasers.

The Talbot effect, a well-established phenomenon in optics, has been a subject of extensive research for many years. Recently, there has been growing interest in its periodic revival within periodically structured light fields during free propagation, driving innovative advancements in spatial, temporal, and space-time Talbot effects. However, studies of the Talbot effect in such structured light fields have remained confined to two-dimensional configurations in the X-T plane, with no exploration of multidimensional structured light fields. In this paper, we propose a new class of three-dimensional periodic structured light fields that exhibit the Talbot effect in full space-time. With an additional dimension given, full space-time Talbot light fields with different properties, such as uneven spatiotemporal Talbot effect, carrying longitudinal orbital angular momentum, and spatiotemporal spiral light fields are studied. In the future, this new type of space-time light field with multidimensional control may lead to new properties and a broader range of potential applications.

Spatiotemporal optical vortex reconnections between two and three vortices in a wavepacket can occur under propagation with diffraction or dispersion.

Objective The optical orbital angular momentum ( OAM) can exist either as longitudinal OAM in the spatial vortex beam or transverse OAM in the spatiotemporal optical vortices. In contrast to the amount of research focused on longitudinal OAM, very few pay attention to optical fields with transverse OAM. Unlike longitudinal OAM which is only affected by diffraction, transverse OAM can be affected by both diffractive effect and dispersive effect. One of the biggest challenges in utilizing optical fields carrying transverse OAM is to overcome diffraction and dispersion as the optical field propagates. Diffraction and dispersion will cause the fields to spread in space and time, which limits the applications of the optical field with OAM. We introduce a class of three-dimensional (3D) spatiotemporal localized wave packets with transverse optical OAM. The combination of the transverse OAM and the localized waves enables it to be immune to both dispersion and diffraction as the wave packet propagates. 3D spatiotemporal localized wave packets carrying transverse OAM provide a new opportunity for the utilization of transverse OAM and are expected to be applied in optical communication, quantum optics, and other fields in the future. Methods In previous studies, the vortex phase is placed in the spatial x-y plane and the resulting localized wave packet carries longitudinal OAM. In this study, we rotate the polar axis by 90 degrees, so that it is now aligned in the y- direction. Therefore, the vortex phase term e(im phi) locates in the x-t plane. Two spatiotemporal localized wave packets carrying two types of OAM: longitudinal OAM and transverse OAM are plotted ( Fig. 1). Then, the theoretical derivation [Eqs. ( 4).(6)] proves that the transverse OAM possessed by each photon is m.. In Fig. 2, 3D spatiotemporal localized wave packets described by Eq. (7) with different orders are presented. From the basic-order to higher- order 3D spatiotemporal localized wave packets with transverse OAM, a kind of 3D spatiotemporal localized wave packets in abnormal medium is proposed. Results and Discussions To investigate the localized property, we choose one of the family of 3D localized wave packets and simulate its propagation in a virtual medium BK7 with negative material dispersion (beta(2)= - 25.26 fs(2) mm(-1)) at the central wavelength of 1550 nm. As a comparison, we filter out the central lobe of the wave packet and propagate it in the same medium. Due to the condition that the effects of diffraction and dispersion are equalized, a proper pulse duration and beam size of the filtered wave packet is 112.25 fs and 0.30 mm at L =0 mm, respectively. Hence, we have diffractive length and dispersive length around L-diff = L-dis =180 mm. As shown in Figs. 3 and 4, the spatiotemporal localized wave packet keeps its intensity shape without any distorts during propagation. It is noted that the central lobe wave packet experiences dramatic change and is magnified proportionally in intensity profile compared with the spatiotemporal localized wave packet. The propagation invariability of spatiotemporal localized wave packets has been presented. The ability of the wave packet to propagate free of diffraction/dispersion is only valid when the diffraction effect and the dispersion effect are balanced with each other. In other words, the wave packets propagate unstably in the unbalanced diffraction and dispersion. In addition, the localized capacity cannot be continued permanently due to finite energy in practice. However, the limited invariantly propagated length is longer than the length of the filtered wave packets. On the other side, self-healing is also often used to characterize non-spreading wave packets, leading to a wavefront reconstruction after an electromagnetic absorption obstacle. To verify the self- healing of the spatiotemporal localized waves, we numerically simulate that a rectangular plate ( around widths of 600 mu m) perfectly absorbing electromagnetic fields is placed in the central part of the spatiotemporal localized wave packet and propagate the blocked wave in BK7 (beta(2)= - 25.26 fs2 mm-1). 3D iso-intensity profile of the blocked wave packet in anomalous medium at different propagated lengths ( 0, 230, 320, and 500 mm) is shown in Fig. 5. We can see that the up blocked area and the down area are split into two rings and move towards to the central part in Fig. 5( d). In the end, the wave packets can be recovered to their original spatiotemporal localized wave packets. The linear momentum density and intensity distribution of the blocked wave packet at different propagated distances in y - t plane are shown in Figs. 5( e). 5( h). The direction of linear momentum density is labelled by arrows and points to the blocked areas visually indicating the reason why self-healing can happen in the spatiotemporal localized wave packets. Conclusions In summary, we present a new class of 3D spatiotemporal localized wave packets carrying transverse optical OAM. These wave packets exist in abnormal dispersion and can propagate invariantly when the diffractive effect and the dispersive effect are equal. To investigate the non-spreading nature of these wave packets, we simulate a wave packet (l, m)= (2,1) propagating in a proper and real medium BK7 glass. The results show that the wave packet propagates over several Rayleigh lengths while keeping its structure invariant. The wave packet can be recovered to its origin even when passing through a blocked obstacle. This kind of wave packets may provide new applications related to transverse OAM in the fields such as quantum optics and optical communications.

Spectral filters have been regularly used in fiber lasers to stabilize the mode-locking. This abstract is to present the recent progress of mode-locked operations in fiber lasers with various spectral filtering schemes.