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Herein, the lasing action of fabricated bulged CH3NH3PbBr3 microwires is demonstrated with features of a low threshold, narrow linewidth, single‐mode operation, and high intensity. Benefiting from the bulged end facets, the CH3NH3PbBr3 microwires are feasible for constructing a high‐brightness, whispering‐gallery‐mode(WGM)‐type, and single‐mode laser while suppressing Fabry–Pérot‐type multi‐mode lasing. Numerical simulation unveils that the bulged end facets result in the significantly reduced reflectivity of fundamental waveguided modes. The obtained microlasers require neither complex structures (such as distributed Bragg reflector) nor careful pumping adjustment, suggesting the practical feasibility of a higher single‐mode lasing intensity than conventional WGM perovskite microlasers. The results provide new routes to realize high‐performance perovskite microlasers and their potential application in sensing refractive index. [ABSTRACT FROM AUTHOR]

Efficient mode conversion is crucial for hybrid photonic systems. We present efficient light transition from a standard single-mode fiber (SMF) to a subwavelength-diameter microfiber via a relatively short tapered fiber. Numerical simulations were performed to design the tapered morphology with high transmittance (approximately 86%) for the fundamental modes. The designed tapered fiber was successfully fabricated on the top of a cleaved SMF tip by the direct laser writing (DLW) method. For the 1550 nm wavelength, the transmittance from the standard SMF to the subwavelength-diameter microfiber was determined to be 77%, accompanied by a change in the effective mode area from 38 μm2 to 0.47 μm2 within a very short length of 150 μm. Our result demonstrated the versatility of the DLW technique for boosting the mode conversion efficiency of fiber-to-chip devices, enabling various applications in the future. [ABSTRACT FROM AUTHOR]

A new on‐chip diagnostic tool is developed, allowing for real‐time full characterization of waveguided ultrashort optical pulses. This technique, called transverse frequency‐resolved optical gating (T‐FROG), relies on second harmonic generation (SHG) in a transverse (surface emitting) geometry. The T‐FROG is implemented on a thin‐film lithium niobate (LN) platform, demonstrating its versatility and consistency in accurately characterizing waveguided femtosecond pulses, including information about chirp and self‐phase modulation. In contrast to traditional FROG techniques, T‐FROG represents a significant improvement as it provides temporal amplitude and phase profiles of ultrafast optical pulses directly inside photonic integrated circuits. The real‐time in situ characteristics and dynamics of optical pulses offered by T‐FROG show promise for their potential applications in the design, testing, and optimization of ultrafast photonic integrated circuits. [ABSTRACT FROM AUTHOR]

In this work, a facile and versatile strategy for the synthesis of contorted polycyclic aromatic hydrocarbons (PAHs) starting from the functionalized pentacene was established. A series of novel PAHs 1–4 and their derivatives were synthesized through a simple two‐step synthesis procedure involving an intramolecular reductive Friedel–Crafts cyclization of four newly synthesized pentacene aldehydes 5–8 as a key step. All the molecules were confirmed by single‐crystal X‐ray diffraction and their photophysical and electrochemical properties were studied in detail. Interestingly, the most striking feature of 1–4 is their highly contorted carbon structures and the accompanying helical chirality. In particular, the optical resolution of 2 was successfully achieved by chiral‐phase HPLC, and the enantiomers were characterized by circular dichroism and circularly polarized luminescence spectroscopy. Despite the highly nonplanar conformations, these contorted PAHs exhibited emissive properties with moderate‐to‐good fluorescence quantum yields, implying the potential utility of this series PAHs as high‐quality organic laser dyes. By using a self‐assembly method with the help of epoxy resin, a bottle microlaser based on 3 a was successfully illustrated with a lasing wavelength of 567.8 nm at a threshold of 0.3 mJ/cm2. We believe that this work will shed light on the chemical versatility of pentacene and its derivatives in the construction of novel functionalized PAHs. [ABSTRACT FROM AUTHOR]

Bending losses of nanofibers or nanowires with circular 90[degrees] bends are simulated using a three-dimensional finite-difference time-domain (3D-FDTD) method. Dependences of bending losses on wavelength and polarization of guided light are investigated, as well as the diameters, refractive indices, and bending radii of nanowires. The acceptable bending losses (~1 dB/90[degrees]) predicted in glass, polymer, and semiconductor nanowires with bending radii down to micrometer level may offer valuable references for assembling highly compact photonic integrated circuits or devices with optical nanowires. OCIS codes: 060.2310, 230.7370, 350.3950.

Newly emergent type-II Weyl semimetals with topological surface states so-called Fermi arcs have attracted much attention for their novel physical properties and potential application in quantum devices. Here, we investigate the in-plane anisotropic structure and inversion symmetry breaking by angle-resolved polarized Raman and second harmonic generation and observe the anisotropic Shubnikov-de Haas effect in Weyl Semimetal MoTe2, which is only present in the b-axis (armchair chain) direction. First-principles calculation depicts the type-II Weyl points and clear topological Fermi arcs. A nontrivial π Berry's phase from Landau quantization and an extra-quantum oscillation frequency arising by Weyl orbit are obtained, which provide evidence for the existence of an anisotropic type-II Weyl state in MoTe2. This work reveals the nontrivial topological surface state of Weyl semimetal MoTe2 in both theory and experiment, providing a promising platform for unique physical properties and applications in quantum information processing. [ABSTRACT FROM AUTHOR]

Chemically synthesized metal nanowires are promising building blocks for next-generation photonic integrated circuits, but technological implementation in monolithic integration will be severely hampered by the lack of controllable and precise manipulation approaches, due to the strong adhesion of nanowires to substrates in non-liquid environments. Here, we demonstrate this obstacle can be removed by our proposed earthworm-like peristaltic crawling motion mechanism, based on the synergistic expansion, friction, and contraction in plasmon-driven metal nanowires in non-liquid environments. The evanescently excited surface plasmon greatly enhances the heating effect in metal nanowires, thereby generating surface acoustic waves to drive the nanowires crawling along silica microfibres. Advantages include sub-nanometer positioning accuracy, low actuation power, and self-parallel parking. We further demonstrate on-chip manipulations including transporting, positioning, orientation, and sorting, with on-situ operation, high selectivity, and great versatility. Our work paves the way to realize full co-integration of various functionalized photonic components on single chips. Implementing metal nanowires in photonic circuits is challenging due to lack of suitable manipulation techniques. Here, the authors present an earthworm-like peristaltic crawling motion mechanism, based on surface plasmons and surface acoustic waves, and show on-chip manipulations of single nanowires. [ABSTRACT FROM AUTHOR]

The ability to manipulate microlaser performance is highly desirable so as to promote on-chip classical and quantum information-processing technology. Here, we demonstrate that mode manipulation of bottle microresonators is enabled by precise deposition of single gold nanoparticles in a reconfigurable and selective manner. Numerical investigation reveals the mechanism of introducing optical loss via single Au NP scattering. Experimental results show that the lasing action of cavity modes could be efficiently suppressed, and single mode lasing is successfully achieved with a high side mode suppression factor ∼13 dB. [ABSTRACT FROM AUTHOR]

Herein, we report a two-step solution-precipitation approach to synthesize perovskite CH3NH3PbBr3 polyhedral single crystals. Their formation mechanism was investigated, revealing the close relationship between reaction rate and crystallization of perovskite. Furthermore, such perovskite polyhedrons were demonstrated to be feasible for lasing with a high quality factor and for single-mode operation. [ABSTRACT FROM AUTHOR]

Abstract: Layered GaSe flakes have revealed strongest second‐harmonic (SH) generation among all the two‐dimensional (2D) atomic crystals measured up to now. However, the unique feature of physical atomic thickness at nanometer scale prevents their practical applications in efficient nonlinear optical conversion due to limited light–matter interaction length. In this work, high quality single‐crystal GaSe nanoribbons (NRs) are fabricated and demonstrated as waveguides with good performance. By taking advantage of the strong confinement and long interaction length of the waveguiding approach, significantly enhanced nonlinear light–matter interaction is observed in GaSe NRs. Based on transverse SH generation, a single GaSe NR‐configured optical auto‐correlator is constructed for ultrashort pulse characterization. Because of the large second‐order nonlinear susceptibility, high sensitivity down to few femto‐joule (fJ) is realized. To the best of our knowledge, this is the highest energy sensitivity among the reported nanoscale auto‐correlators. Such NR waveguides and devices are highly compatible with standard optical fiber systems. The presented results may enable the construction of future energy efficient nonlinear photonic circuitry, chips, and devices. [ABSTRACT FROM AUTHOR]

Integrationof miniaturized elements has been a major driving forcebehind modern photonics. Nanowires have emerged as potential buildingblocks for compact photonic circuits and devices in nanophotonics.We demonstrate here a single nanowire optical correlator (SNOC) forultrafast pulse characterization based on imaging of the second harmonic(SH) generated from a cadmium sulfide (CdS) nanowire by counterpropagatingguided pulses. The SH spatial image can be readily converted to thetemporal profile of the pulses, and only an overall pulse energy of8 μJ is needed to acquire a clear image of 200 fs pulses. Sucha correlator should be easily incorporated into a photonic circuitfor future use of on-chip ultrafast optical technology. [ABSTRACT FROM AUTHOR]

We report broad spectral response in composition-graded CdSSe single nanowires (NWs) via waveguiding excitation. The excitation light is coupled to CdSSe single nanowires via silica fiber tapers. The guided photons in the nanowire with energies ranging from 1.74 to 2.44 eV can be efficiently captured at different sites along the NW length. Compared to single-composition nanowires, the composition-graded CdSSe nanowires exhibit much broader spectral response range, while retaining the detection limit down to sub-pW level. Utilizing the photoconductive quenching effect, the spectral range can be further extended beyond 1.5 μm with detection limit down to sub-nW level at room temperature. [ABSTRACT FROM AUTHOR]

We demonstrated a pigtailed nanoribbon ring laser constructed with a 600 nm wide and 330 nm thick CdS nanoribbon. When the 20-μm-diameter ring was irradiated by light from a supercontinuum source, multi longitudinal mode laser emission was observed around 523.5 nm with full widths at half maximum of 0.27 nm. The laser output from the pigtail showed strong orientation-dependent polarization, with a maximum polarization ratio of 5 and power up to 3.7 nW. [ABSTRACT FROM AUTHOR]

It is highly desirable to design optical devices with diverse optomechanical functions. Here, we investigate lateral optical force exerted on subwavelength-diameter (SD) optical fibers harnessed by input light modes with different polarizations. It is interesting to find that input light modes of circular or elliptical polarizations would bring about lateral optical force in new directions, which has not been observed in previous studies. By means of finite-difference time-domain (FDTD) simulations, detailed spatial distributions of the asymmetric transverse force density are revealed, meanwhile dependence of optical force on input light polarizations, fiber diameters, and inclination angles of fiber endfaces are all carefully discussed. It is believed that polarization-sensitive reflection, refraction, and diffraction of optical fields occur at the interface, i.e., fiber oblique endfaces, resulting in asymmetrically distributed optical fields and thereafter non-zero transverse optical force. We believe our new findings could be helpful for constructing future steerable optomechanical devices with more flexibility. [ABSTRACT FROM AUTHOR]

Meeting the challenges of realizing organic electrically pumped laser, low threshold gain materials with minimum optical loss are highly demanded, especially those with insignificant nonradiative processes during lasing. Herein, the low optical loss amplified spontaneous emission (ASE) and high Q‐factor (2,700) lasing are discovered in a solution‐processed benzothiadiazole‐cored multifluorene derivative. The excellent lasing properties of this molecule inspire to focus on the origin of its intrinsic optical loss. The ultrafast time‐resolved spectroscopy studies reveal that the low intrinsic optical loss originates from a relatively "simple" excited state interaction including just singlet–singlet absorption and stimulated emission, excluding additional loss processes such as intermolecular charge‐separation and triplet–triplet absorption that are detrimental to achieve high quality lasing. Quantitative descriptions on ASE process are also discussed based on both transient absorption spectra and transient photoluminescence spectra. This study shows new options and deeper understanding for designing low threshold gain materials. [ABSTRACT FROM AUTHOR]

Newly emergent type-II Weyl semimetals with topological surface states so-called Fermi arcs have attracted much attention for their novel physical properties and potential application in quantum devices. Here, we investigate the in-plane anisotropic structure and inversion symmetry breaking by angle-resolved polarized Raman and second harmonic generation and observe the anisotropic Shubnikov-de Haas effect in Weyl Semimetal MoTe2, which is only present in the b-axis (armchair chain) direction. First-principles calculation depicts the type-II Weyl points and clear topological Fermi arcs. A nontrivial π Berry's phase from Landau quantization and an extra-quantum oscillation frequency arising by Weyl orbit are obtained, which provide evidence for the existence of an anisotropic type-II Weyl state in MoTe2. This work reveals the nontrivial topological surface state of Weyl semimetal MoTe2 in both theory and experiment, providing a promising platform for unique physical properties and applications in quantum information processing. [ABSTRACT FROM AUTHOR]

With the development of laser technology, nonlinear optics plays a crucial role in frequency conversion. However, the generation of second harmonics in nonlinear optical crystals is generally subject to rigorous phase-matching conditions that hinder the performance of broadband tunability. It is believed that introducing disorders in nonlinear optical materials is helpful to overcome this obstacle. In this work, we have prepared a nonlinear microcrystal-doped glass (NMG) composite material, allowing for tunable and polarization-independent nonlinear conversion from visible to near-infrared. The linear dependence of SHG intensity versus sample thickness indicated the facilitation of random quasi-phase matching by using the NMG. Our results provide a more stable and promising platform for disordered nonlinear photonic materials and suggest the possibility of more efficient nonlinear conversions using the NMG composite glass fibers in future.

We report a femtosecond Kerr-lens mode-locked (KLM) Alexandrite laser resonantly pumped by a 589 nm yellow laser. The 4 nJ pulses as short as 42 fs were obtained corresponding to a peak power of 100 kW. With the repetition rate of 104 MHz, the average power of 420 mW was attained. The time-bandwidth product of generated laser pulse was measured to be 0.324 with a beam quality factor of M 2  ≤ 1.13. The exceptional performance of visible femtosecond laser may find potential applications in various fields.

We demonstrated a compact and power-efficient multi-stage pulsed end-pumped amplifier with stabilized output power of 450 W and near-diffraction-limited beam quality (M 2  < 1.2) at a repetition rate of 1 MHz. The pulsed amplifier produced an exceptional average power and optimal beam quality achieved in laser diode (LD) end-pumped Yb:YAG thin rod configuration at room temperature. A preliminary pulse compression with a chirped volume Bragg grating (CVBG) was performed reducing pulse duration to ∼730 fs at a compression efficiency of 90%. With the combined features, including compactness, reliability, and efficiency, of the end-pumped scheme, the demonstrated laser system would be of great value in both industry and scientific research.

We demonstrate a Ti:Sapphire laser generating in excess of 1.2 W in continuous-wave operation when pumped directly with four green laser diodes eliminating the need for a complex pump laser. As a result, improvement of laser efficiency is achieved without sacrificing beam quality. Tunability within the range of 740-840 nm is attained validating the concept of a direct laser-diode pumped Ti:Sapphire laser.

An optical spectrometer is a basic spectral instrument that probes microscopic physical and chemical properties of macroscopic objects but generally suffers from difficulty in broadband time-resolved measurement. In this work, we report the creation of ultrabroadband white-light laser with a 3-dB bandwidth covering 385 to 1,080 nm, pulse energy of 1.07 mJ, and pulse duration of several hundred femtoseconds by passing 3-mJ pulse energy, 50-fs pulse duration Ti:Sapphire pulse laser through a cascaded fused silica plate and chirped periodically poled lithium niobate crystal. We utilize this unprecedented superflat, ultrabroadband, and intense femtosecond laser light source to build a single-shot (i.e., single-pulse) subpicosecond pulse laser ultraviolet-visible-near-infrared spectrometer and successfully measure various atomic and molecular absorption spectra. The single-shot ultrafast spectrometer may open up a frontier to monitor simultaneously the ultrafast dynamics of multiple physical and chemical processes in various microscopic systems., (Copyright © 2023 Lihong Hong et al.)

3,6-Carbazole precursors were used to prepare an octaphyrin. The conformation and electronic structure of the system could be modulated through trifluoroacetate (TFA) protonation and BF 2 complexation. The resulting nonaromatic macrocyclic complexes, 2-2TFA and 2-2BF 2 , displayed noteworthy photophysical properties. For instance, the diprotonated species 2-2TFA showed a strong panchromic absorption up to 800 nm, while the bis-BF 2 -chelated dipyrromethene (BODIPY)-like complex 2-2BF 2 exhibited an intense visible absorption feature (ε 535nm = 2.1 × 10 5 M -1 cm -1 ), as well as a relatively red-shifted emission at 640 nm characterized by a large Stokes shift. It was found that 2-2BF 2 could be used to construct a high-quality organic microlaser that functions under optical pumping. The present study highlights the potential utility of expanded porphyrins as possible laser dyes.

Instantaneous control over the orientation of anisotropically shaped plasmonic nanostructures allows for selective excitation of plasmon modes and enables dynamic tuning of the plasmonic properties. Herein we report the synthesis of rod-shaped magnetic/plasmonic core-shell nanocomposite particles and demonstrate the active tuning of their optical property by manipulating their orientation using an external magnetic field. We further design and construct an IR-photoelectric coupling system, which generates an output voltage depending on the extinction property of the measured nanocomposite sample. We employ the device to demonstrate that the nanocomposite particles can serve as units for information encryption when immobilized in a polymer film and additionally when dispersed in solution can be employed as a new type of magnetic-field-direction sensor., Competing Interests: The authors declare that there are no conflicts of interest regarding the publication of this article.

We investigate transverse optical forces exerted on the endface of subwavelength-diameter (SD) optical fiber by using a finite-difference time-domain (FDTD) method. Detailed spatial distributions of transverse optical force along the fiber axis can now be accessible, based on which the dependence of transverse optical force on transverse cross sections, oblique-cut endfaces and high-order mode are carefully studied. Our numerical results demonstrate that either asymmetric cross section or oblique-cut endface would dominantly contribute to the transverse optical force and the corresponding sideways deflection of SD fiber, which is in good agreement with previous experimental observations. The novel behavior of transverse optical force by the high-order mode would give rise to new guidelines for constructing high-performance optomechanical devices.

Organometal halide perovskite has recently emerged as a very promising family of materials with augmented performance in electronic and optoelectronic applications including photovoltaic devices, photodetectors, and light-emitting diodes. Herein, we propose and demonstrate facile solution synthesis of a series of colloidal organometal halide perovskite CH3NH3PbX3 (X = halides) nanoparticles with amorphous structure, which exhibit high quantum yield and tunable emission from ultraviolet to near-infrared. The growth mechanism and photoluminescence properties of the perovskite amorphous nanoparticles were studied in detail. A high-efficiency green-light-emitting diode based on amorphous CH3NH3PbBr3 nanoparticles was demonstrated. The perovskite amorphous nanoparticle-based light-emitting diode shows a maximum luminous efficiency of 11.49 cd/A, a power efficiency of 7.84 lm/W, and an external quantum efficiency of 3.8%, which is 3.5 times higher than that of the best colloidal perovskite quantum-dot-based light-emitting diodes previously reported. Our findings indicate the great potential of colloidal perovskite amorphous nanoparticles in light-emitting devices.

Controlling nonlinear light-matter interaction is important from a fundamental science point of view as well as a basis for future optoelectronic devices. Recent advances in two-dimensional crystals have created opportunities to manipulate nonlinear processes electrically. Here we report a strong second-harmonic generation (SHG) in a 2D WSe2 bilayer crystal caused by a back gate field. This unusual process takes place only when the gate polarity causes charge accumulation rather than depletion. Analysis based on a bond-charge model traces the origin of SHG to the nonuniform field distribution within a single monolayer, caused by the accumulated submonolayer screening charge in the tungsten plane. We name this phenomenon charge-induced SHG (CHISHG), which is fundamentally different from the field- or current-induced SHG. Our findings provide a potentially valuable technique for understanding and noninvasive probing of charge and current distributions in future low dimensional electronic devices.

Multicolour lasing with wavelength varying from 578 nm to 640 nm is realized from a single bandgap-graded CdSSe alloy nanoribbon, by selecting the excited spot at room temperature. Though reabsorption is a serious problem to achieve lasing at short wavelength, multiple scatters on the nanoribbon form localized cavities, and thus lasing at different wavelengths is realized. By increasing the excitation area, multicolour lasing from the same nanoribbon is also observed simultaneously.

We report the first observation of supercontinuum (SC) generation in single semiconductor nanoribbons (NRs). By launching a continuous wave (CW) 532-nm pump light along a 200-μm-length CdS NR for waveguiding excitation, SC generation is realized with a threshold down to sub-milliwatt level, which is ~3 orders lower compared with previous CW-pumped SC generated in glass fibers. The low threshold is benefitted from the favorable material properties and waveguide geometries including high Raman gains, strong light confinement, more optical guided modes and phonon modes. Our work paves the way to low-threshold nanoscale SC sources and may find widespread applications ranging from spectroscopic analysis and biological imaging to material research.

We report a microfibre absorption sensor by using a 900 nm diameter silica microfibre embedded in a 125 μm wide microchannel with a detection length of 2.5 cm. Investigated by measuring the absorbance of methylene blue (MB), the sensor shows a detection limit down to 50 pM with excellent reversibility in a concentration range of 0-5 nM. The sensor has also been applied to bovine serum albumin (BSA) measurement, with a detection limit of 10 fg mL(-1). In addition, the sample volume requirement is merely 500 nL with a probing light power of about 150 nW, which is very promising for safe detection of single or a few molecules of biological specimens., (This journal is © The Royal Society of Chemistry 2011)

A large defect-induced sub-bandgap photoresponse over a broad spectral range is observed in semiconductor single nanowires via optical waveguiding excitation. Using an evanescent coupling technique, the excitation sub-bandgap light is efficiently transferred from a silica fiber taper into a CdS single nanowire (bandgap ∼ 2.46 eV), and is tightly confined and guided through the whole length of the nanowire, which significantly enhances the light-defect interaction compared with the conventional irradiation excitation scheme. Under 593 nm wavelength (∼2.09 eV) waveguiding excitation with an input power of 10 pW level at room temperature, a 350 nm diameter 150 µm-length CdS nanowire shows a responsivity of 250 A W( - 1), offering a sub-bandgap photosensitivity five orders of magnitude larger than by irradiation excitation. These results may open opportunities for noninvasive characterization of defect states in semiconductor nanowires, as well as for enabling novel sub-bandgap nanowire devices.

We fabricate fiber Bragg grating (FBG) in microfibers (MFs) using focused ion beam milling technique. By periodically etching 100 nm-depth grooves on the surface of silica MFs with diameters less than 2 μm, evident grating features with transmission dip up to 15 dB are obtained. Because of the high-index contrast of the gratings structure, the length of the microfiber Bragg grating (MFBG) can be reduced to 500 μm level. Using a 518 μm-length 1.8 μm-diameter MFBG, we also demonstrate sensitivity up to 660 nm per refractive index unit (RIU) for refractive index (RI) sensing. The highly compact MFBGs demonstrated here may serve as low-dimensional building blocks for miniaturized photonic components and devices., (© 2011 Optical Society of America)

We demonstrate broadband optical quenching of photoconductivity in CdSe single nanowires with low excitation power. Using 1550-nm-wavelength light with 10-nW power for waveguiding excitation, we observe a typical responsivity of 0.5 A/W for quenching the photoconductivity established by 10-µW 660-nm-wavelength background light in a 403-nm-diameter CdSe nanowire, with detectable limit of the quenching power down to pW level at room temperature, which is several orders of magnitude lower than those reported previously. This large quenching effect originates from the enhanced light-defect interaction in the nanowires via waveguiding excitation. These results open new opportunities for noninvasive characterization of deep-level defect states in low-dimensional semiconductor nanomaterials, and novel optoelectronic applications of semiconductor nanowires such as high-sensitive broadband photodetection.

We demonstrate single-mode laser emission in single nanowires. By folding a 200 nm diameter CdSe nanowire to form loop mirrors, single-mode laser emission around 738 nm wavelength is obtained with line width of 0.12 nm and low threshold. The mode selection is realized by the vernier effect of coupled cavities in the folded nanowire. In addition, the loop structure makes it possible to tune the nanowire cavity, opening an opportunity to realize a tunable single-mode nanowire laser.

We demonstrate whispering gallery (WG) resonance of surface plasmon polaritons (SPPs) in a 2-dimensional confined Au cylinder by self interference. Despite the leakage of SPPs along the axis of the cylinder, Q factors of 375 are obtained in a cylinder with diameter of 30 μm. The coupling-angle-dependence of the WG resonance is also investigated. Our results open opportunities for a new category of plasmonic cavities with 2-dimensional confinement, and this may be applied to a variety of simple and natural metallic micro or nanostructures.

Bandgap engineering of semiconductor nanowires is important in designing nanoscale multifunctional optoelectronic devices. Here, we report a facile thermal evaporation method, and realize the spatial bandgap engineering in single CdS(1-x)Se(x) alloy nanowires. Along the length of these achieved nanowires, the composition can be continuously tuned from x = 0 (CdS) at one end to x = 1 (CdSe) at the other end, resulting in the corresponding bandgap (light emission wavelength) being modulated gradually from 2.44 eV (507 nm, green light) to 1.74 eV (710 nm, red light). In spite of the existing composition (crystal lattice) transition along the length, these multicolor nanowires still possess high-quality crystallization. These bandgap engineered nanowires will have promising applications in such as multicolor display and lighting, high-efficiency solar cells, ultrabroadly spectral detectors, and biotechnology.