We demonstrated experimentally an on-chip Fourier transform spectrometer based on an ultra-low half-wave voltage electro-optic modulator fabricated on thin film lithium niobate platform. The ...spectrometer has a pair of identical folded modulation arms with a waveguide length of 15.34 cm and an electrode length of 11.2 cm, showing a half-wave voltage as low as 0.266 V at 1550 nm wavelength. The wavelength-dependent losses of the fabricated spectrometer were measured and hence the transfer function of the spectrometer was obtained. Further, by applying a ramp voltage ranging from −100 V to 100 V to the electrodes, the intensity-voltage interferogram was obtained with a photodetector. The spectrum of the input light was retrieved by performing a Fourier transform on the interferogram combined with the wavelength-dependent equation of the half-wave voltage of the spectrometer. The results indicate that our fabricated spectrometer can achieve a resolution of 5.32 nm, an operation bandwidth beyond 100 nm, and a sub-microsecond measurement time.
A new noncentrosymmetric (NCS) quaternary sulfide, SrAgAsS4, was obtained via the strategy of aliovalent substitution based on centrosymmetric (CS) SrGa2S4. The new compound features two-dimensional ...AgAsS42– layers, which are composed of alternately connected AsS4 tetrahedra and AgS4 tetrahedra. Importantly, SrAgAsS4 exhibits a strong phase-matched second-harmonic generation response (1.35 × AgGaS2 at 2100 nm) and has a suitable birefringence (0.15@2100 nm) and moderate band gap (2.31 eV). The first-principles calculations revealed the significant contribution of AsS4 and AgS4 tetrahedra to its optical properties. This work will promote the application of the aliovalent substitution strategy in the design of NCS-structure-based functional materials.
Metal thiophosphates have outstanding properties for the generation of mid-infrared coherent light and are an emerging nonlinear optical material system. In this study, a new non-centrosymmetric ...(NCS) quaternary alkaline-earth metal thiophosphate, SrAgPS4, was obtained via a high-temperature solid-state method. The new compound crystallizes in the NCS Ama2 (No. 40) space group and features two-dimensional AgPS42− layers consisting of alternately connected PS4 and AgS4 tetrahedra. SrAgPS4 exhibits a strong phase-matched second harmonic generation response (1.10 × AgGaS2 at 2100 nm) and a large band gap (2.97 eV). In addition, theoretical calculations reveal the intrinsic relationship between the electronic structure and optical properties. This work enriches and greatly promotes the research on infrared nonlinear optical materials based on thiophosphates.
High-sensitivity and miniature volatile organic compound (VOC) sensor is considerably significant for environment monitoring. Herein we performed the theoretical and experimental optimization of ...waveguide sensor to realize the sensitive detection of volatile toxic pyridine vapor with ppb-level detection limit. The miniature sensor is based on the CMOS-compatible silicon nitride (Si3N4) Mach-Zehnder interferometer (MZI) waveguide with dipolar polycarbonate as sensitive cladding material. Theoretical optimization by varying the waveguide width and the thickness of sensitive cladding is carried out to tune the group refractive index and evanescent field. Experimentally, two MZIs with distinct waveguide widths and sensitive cladding thickness are fabricated to compare their performance in pyridine vapor sensing. The sensing results show that the thickness of sensitive layer plays a key role in sensing sensitivity and response time. The final obtained pyridine sensing sensitivity can reach 63 pm/ppm and the detection limit can be as low as 476 ppb. Our demonstration provide a simple and efficient strategy for sensitive sensing of hazardous chemical vapors, which may find application in biochemical sensing.
•The hybrid integrated waveguide of Si3N4 and functional polymer was fabricated for volatile pyridine vapor sensing.•High-sensitivity Si3N4/polymer hybrid Mach-Zehnder interferometer sensor was design.•Pyridine sensing with high sensitivity of 63 pm/ppm and low detection limit of 476 ppb is achieved.•The thickness of sensitive polymer cladding plays key role in sensitivity and response speed.
Metal chalcogenides play a critical role in the infrared (IR) nonlinear optical (NLO) field. However, Eu-based chalcogenide-type IR NLO materials are still scarce up to now. In this paper, two new ...quaternary Eu-based chalcogenides, EuHgGeSe4 and EuHgSnS4, containing the “NLO active groups” HgQ46– (Q = S, Se) and GeSe44–/SnS44– were synthesized through traditional high-temperature solid-state reactions. They possess noncentrosymmetric structures, crystallizing in the Ama2 space group, and exhibit strong phase-matchable second-harmonic-generation (SHG) responses (3.1× and 1.77× that of AgGaS2 for EuHgGeSe4 and EuHgSnS4, respectively). Meanwhile, the optical band gaps of EuHgGeSe4 (1.97 eV) and EuHgSnS4 (2.14 eV) were determined from UV–vis–NIR diffuse reflectance spectra. Differential scanning calorimetry (DSC) analyses reveal the congruent-melting behavior of EuHgGeSe4. Furthermore, structural analysis and theoretical calculations verify the critical driving effects of HgQ46– tetrahedra on the strong SHG activity. The overall results demonstrate that EuHgGeSe4 and EuHgSnS4 are potential IR NLO materials.
We propose an electro-optic mode-selective switch based on cascaded three-dimensional lithium-niobate waveguide directional couplers fabricated with a single-step annealed proton-exchange process. To ...compensate for discrepancies due to uncertainties in the fabrication process, we develop a post-tuning technique to improve the performance of the coupler by means of depositing a layer of titanium oxide (TiO
) onto one of the waveguides of the coupler. By integrating two cascaded dissimilar directional couplers, we experimentally demonstrate switchable (de)multiplexing of the LP
, LP
, and LP
modes, where the LP
mode can be switched at an efficiency over 75% from 1530 nm to 1612 nm with an applied voltage varying between -9 V and +30 V, and the LP
mode can be switched at an efficiency higher than 90% from 1534 nm to 1577 nm with an applied voltage varying between -21 V to 0 V. The switching times are 230-300 ns. Our proposed waveguide platform could be employed to develop advanced switches for applications in areas where high-speed switching of spatial modes is required, such as reconfigurable mode-division-multiplexing communication.
Inorganic metal chalcohalides, as significant semiconductor materials, have emerged as promising candidates for photoelectric applications. Herein, a new type of quaternary chalcohalide, Ba
4
XIn
19
...S
32
(X = Cl, Br), has been discovered using the high-temperature halide salt flux method. Single-crystal X-ray diffraction analysis reveals that they are isostructural and crystallize in the tetragonal space group
I
4
1
/
amd
(no. 141) featuring the octahedral hole formed by six InS
4
5−
tetrahedra filled with a ClBa
4
7+
polycation, surrounded by a three-dimensional covalent framework formed by interconnecting InS
6
9−
octahedra through corner-sharing and edge-sharing. Moreover, Ba
4
ClIn
19
S
32
and Ba
4
BrIn
19
S
32
exhibit wide optical bandgaps of 2.70 eV and 2.46 eV, respectively, and moderate birefringences (0.044 @ 2100 nm and 0.042 @ 2100 nm, respectively). Specifically, Ba
4
XIn
19
S
32
(X = Cl, Br) display remarkable photocurrent responses under simulated solar-light illumination, implying their potential for photocatalytic applications. Theoretical calculations were employed to understand the interrelationship between the optical properties and electronic structure. The study on the synthesis and structure-property relationship analysis of inorganic metal chalcohalides provides new insight into the exploration of promising photoelectric materials.
Two novel centrosymmetric chalcogenides Ba
4
XIn
19
S
32
(X = Cl, Br) were successfully synthesized and they display remarkable photocurrent responses under simulated solar-light illumination.
In silicon photonic waveguides, the on-chip integration of high-performance nanomaterials is considerably important to enable the waveguide sensing function. Herein, the in situ self-assembly of the ...low refractive index (RI) metal–organic framework nanomaterial ZIF-8 with a large surface area and high porosity on the surface of a designated SiO2 waveguide for evanescent wave sensing is demonstrated. The surface morphology and transmission loss of the nano-functionalized waveguide are investigated. The specific design and fabrication of asymmetric Mach–Zehnder interferometers (AMZIs) are performed based on the optical properties of ZIF-8. Such efforts in waveguide engineering result in an output interfering spectrum of nano-functionalized AMZI with an ultra-high extinction ratio (28.6 dB), low insertion loss (∼13 dB) and suitable free spectral range (∼30 nm). More significantly, the outstanding sensing features of ZIF-8 are successfully realized on the SiO2 waveguide chip. The results of ethanol detection show that the AMZI sensor has a large detection range (0 to 1000 ppm), high sensitivity (19 pm ppm−1 from 0 to 50 ppm or 41 pm ppm−1 from 600 to 1000 ppm) and low detection limit (1.6 ppm or 740 ppb). This combination of nanotechnology and optical waveguide technology is promising to push forward lab-on-waveguide technology for volatile organic compound (VOC) detection.
Two alkaline earth metal-containing thiophosphate compounds, BaAg7(PS4)3 and SrAg7(PS4)3, were synthesized via the homovalent substitution of Pb2+ in PbAg7(PS4)3 by Ba2+ and Sr2+, respectively. The ...space group of BaAg7(PS4)3 (P21/c) and SrAg7(PS4)3 (P63/m) is the same as the low- and high-temperature phases of PbAg7(PS4)3, respectively. The two compounds exhibit structural similarity and possess three-dimensional honeycomb-shaped architectures. These honeycomb structures are arranged in a layered fashion via hexagonal rings, which arise from the sharing of edges or vertices between AgS4 and PS4 tetrahedral, accommodating discrete entities of Ba2+ and Sr2+ cations. BaAg7(PS4)3 melts congruently with a melting point of 760 °C and a solidification point of 675 °C, while the melting behaviour of SrAg7(PS4)3 was incongruently and thermally stable up to 689 °C under vacuum of 1 × 10−3 Pa. Moreover, the band gaps of BaAg7(PS4)3 (2.69 eV) and SrAg7(PS4)3 (2.85 eV) have a significant enlargement compared to PbAg7(PS4)3 (2.09 eV). The combination of d10 cation Ag+ with second-order Jahn-Teller distortion and alkaline earth metals cation enriches the system of new metal thiophosphates and provides ideas for exploring other functional materials.
Two new phosphorothioates, BaAg7(PS4)3 and SrAg7(PS4)3, were prepared by the homovalent substitution of PbAg7(PS4)3, and their space groups corresponded to the low-temperature and high-temperature phases of PbAg7(PS4)3, respectively. Display omitted
•Two new thiophosphates BaAg7(PS4)3 and SrAg7(PS4)3 were prepared by the homovalent substitution of PbAg7(PS4)3.•The space group of BaAg7(PS4)3 and SrAg7(PS4)3 corresponds to the low- and high-temperature phases of PbAg7(PS4)3.•The band gaps of BaAg7(PS4)3 (2.69 eV) and SrAg7(PS4)3 (2.85 eV) are compared with PbAg7(PS4)3 (2.09 eV).
Electro-optic materials at the shortwave infrared window (850 nm) is significant for optical modulation in free-space communication and short-distance local area networks. However, most of the ...current high-performance organic nonlinear optical chromophores (absorption bandgap ∼1.5 eV) are designed for operating at 1310 nm (O band) or 1550 nm (C band) and do not exhibit optical transparency at 850 nm (bandgap ∼1.45 eV). The design and synthesis of chromophores exhibiting optical transparency at 850 nm are more challenging because regular bandgap engineering to improve microcroscopic nonlinearity (
μβ
value) might not be available due to the bandgap restriction (optical transparency) at 850 nm. In this respect, this manuscript utilizes the strategy of suitable site-isolation in molecular engineering to optimize the comprehensive performance of chromophores for electro-optics at 850 nm. Vilsmeier formylation has been facilitated on symmetric or asymmetric donor-π-donor intermediate dyes to form donor-π-acceptor (D-π-A) chromophores C1 and C2 with tunable conjugated steric hindrance (a site-isolator). Without significant red-shifts in the absorption spectra, conjugated steric hindrance groups contribute to large enhancement in the
μβ
values of the chromophores and ensure optical transparency at 850 nm. The
μβ
values of C1 (6706 × 10
−48
esu) and C2 (7279 × 10
−48
esu) with conjugated site-isolation groups are much higher than that of previously reported chromophores at 850 nm. The structure-property relationship reveals that a suitable site-isolator is extremely significant for realizing highly efficient translation of microscopic hyperpolarizability into macroscopic electro-optic coefficients. As a result, an electro-optic coefficient of 94 pm V
−1
at 830 nm was achieved. To the best of our knowledge, this is the highest value for organic electro-optic materials at 850 nm.
We show the strategy of introducing a suitable conjugated site-isolator on the bridge of a nonlinear optical chromophore to significantly improve the electro-optic activity at the shortwave infrared window (850 nm) for electro-optic modulation.
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