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Spectroscopy|33 Article(s)
Cavity-enhanced infrared quantum dot homojunction arrays
Naiquan Yan, Feng Shi, Xiaomeng Xue, Kenan Zhang... and Menglu Chen|Show fewer author(s)
Infrared spectroscopy has wide applications in the medical field, industry, agriculture, and other areas. Although the traditional infrared spectrometers are well developed, they face the challenge of miniaturization and cost reduction. Advances in nanomaterials and nanotechnology offer new methods for miniaturizing spectrometers. However, most research on nanomaterial-based spectrometers is limited to the visible wavelength or near infrared region. Here, we propose an infrared spectrometer based on diffraction gratings and colloidal quantum dot (CQD) homojunction photodetector arrays. Coupled with a Fabry-Perot cavity, the CQD photodetector covers the 1.4–2.5 μm spectral range, with specific detectivity 4.64×1011 Jones at 2.5 μm at room temperature. The assembled spectrometer has 256 channels, with total area 2.8 mm×40 mm. By optimizing the response matrix from machine learning algorithms, the CQD spectrometer shows high-resolution spectral reconstruction with a resolution of approximately 7 nm covering the short-wave infrared. Infrared spectroscopy has wide applications in the medical field, industry, agriculture, and other areas. Although the traditional infrared spectrometers are well developed, they face the challenge of miniaturization and cost reduction. Advances in nanomaterials and nanotechnology offer new methods for miniaturizing spectrometers. However, most research on nanomaterial-based spectrometers is limited to the visible wavelength or near infrared region. Here, we propose an infrared spectrometer based on diffraction gratings and colloidal quantum dot (CQD) homojunction photodetector arrays. Coupled with a Fabry-Perot cavity, the CQD photodetector covers the 1.4–2.5 μm spectral range, with specific detectivity 4.64×1011 Jones at 2.5 μm at room temperature. The assembled spectrometer has 256 channels, with total area 2.8 mm×40 mm. By optimizing the response matrix from machine learning algorithms, the CQD spectrometer shows high-resolution spectral reconstruction with a resolution of approximately 7 nm covering the short-wave infrared.
Photonics Research
- Publication Date: May. 27, 2025
- Vol. 13, Issue 6, 1497 (2025)
Erbium as an energy trap center for manipulating NIR-II luminescence of Ho3+ in fluoride towards phonon-based ratiometric thermometry
Mengmeng Dai, Zhiying Wang, Kejie Li, Jiaqi Zhao, and Zuoling Fu
Thermal quenching has been known to entangle with luminescence naturally, which is primarily driven by a multi-phonon relaxation (MPR) process. Considering that MPR and the phonon-assisted energy transfer (PAET) process may interact cooperatively plays a critical role in conducting the thermal response of luminescence thermometry. Herein, an energy mismatch system of Yb3+/Ho3+/Er3+ co-doped β-NaLuF4 hollow microtubes was delicately proposed to combat thermal quenching of near-infrared (NIR)-II luminescence of Ho3+ via premeditated Er3+-mediated PAET processes under 980 nm excitation. Meanwhile, the mechanism of anti-thermal quenching is attributed to the Er3+ as an energy trap center to facilitate the PAET process, thereby enabling a considerable energy transfer efficiency of over 80% between Er3+ and Ho3+ without Yb3+ ions as sensitizers. Leveraging the accelerated PAET process at increased temperature and superior emission, the phonon-tuned NIR-II ratiometric thermometers were achieved based on fluoride beyond the reported oxide host, enabling excellent relative sensitivity and resolution (Sr=0.57% K-1, δT=0.77 K). This work extends the significant effect of PAET on overcoming the notorious thermal quenching, and offers a unique physical insight for constructing phonon-tuned ratiometric luminescence thermometry. Thermal quenching has been known to entangle with luminescence naturally, which is primarily driven by a multi-phonon relaxation (MPR) process. Considering that MPR and the phonon-assisted energy transfer (PAET) process may interact cooperatively plays a critical role in conducting the thermal response of luminescence thermometry. Herein, an energy mismatch system of Yb3+/Ho3+/Er3+ co-doped β-NaLuF4 hollow microtubes was delicately proposed to combat thermal quenching of near-infrared (NIR)-II luminescence of Ho3+ via premeditated Er3+-mediated PAET processes under 980 nm excitation. Meanwhile, the mechanism of anti-thermal quenching is attributed to the Er3+ as an energy trap center to facilitate the PAET process, thereby enabling a considerable energy transfer efficiency of over 80% between Er3+ and Ho3+ without Yb3+ ions as sensitizers. Leveraging the accelerated PAET process at increased temperature and superior emission, the phonon-tuned NIR-II ratiometric thermometers were achieved based on fluoride beyond the reported oxide host, enabling excellent relative sensitivity and resolution (Sr=0.57% K-1, δT=0.77 K). This work extends the significant effect of PAET on overcoming the notorious thermal quenching, and offers a unique physical insight for constructing phonon-tuned ratiometric luminescence thermometry.
Photonics Research
- Publication Date: Apr. 28, 2025
- Vol. 13, Issue 5, 1249 (2025)
Single-photon super-resolved spectroscopy from spatial-mode demultiplexing
Luigi Santamaria, Fabrizio Sgobba, Deborah Pallotti, and Cosmo Lupo
We demonstrate the spectroscopy of incoherent light with subdiffraction resolution. In a proof-of-principle experiment, we analyze the spectrum of a pair of incoherent pointlike sources whose separation is below the diffraction limit. The two sources mimic a planetary system, with a brighter source for the star and a dimmer one for the planet. Acquiring spectral information about the secondary source is difficult because the two images have a substantial overlap. This limitation is solved by leveraging a structured measurement based on spatial-mode demultiplexing, where light is first sorted in its Hermite–Gaussian components in the transverse field then measured by photon detection. This allows us to effectively decouple the photons coming from the two sources. An application is suggested to enhance the exoplanets’ atmosphere spectroscopy. A number of experiments of super-resolution imaging based on spatial demultiplexing have been conducted in the past few years, with promising results. Here, for the first time to the best of our knowledge, we extend this concept to the domain of spectroscopy. We demonstrate the spectroscopy of incoherent light with subdiffraction resolution. In a proof-of-principle experiment, we analyze the spectrum of a pair of incoherent pointlike sources whose separation is below the diffraction limit. The two sources mimic a planetary system, with a brighter source for the star and a dimmer one for the planet. Acquiring spectral information about the secondary source is difficult because the two images have a substantial overlap. This limitation is solved by leveraging a structured measurement based on spatial-mode demultiplexing, where light is first sorted in its Hermite–Gaussian components in the transverse field then measured by photon detection. This allows us to effectively decouple the photons coming from the two sources. An application is suggested to enhance the exoplanets’ atmosphere spectroscopy. A number of experiments of super-resolution imaging based on spatial demultiplexing have been conducted in the past few years, with promising results. Here, for the first time to the best of our knowledge, we extend this concept to the domain of spectroscopy.
Photonics Research
- Publication Date: Mar. 21, 2025
- Vol. 13, Issue 4, 865 (2025)
Tracking and manipulating ultrafast photocarrier dynamics in 3D Dirac semimetal Cd3As2 by chemical doping
Peng Suo, Wenjie Zhang, Yunkun Yang, Long Geng... and Guohong Ma|Show fewer author(s)
Element doping can break the crystal symmetry and realize the topological phase transition in quantum materials, which enables the precise modulation of energy band structure and microscopic dynamical interaction. Herein, we have studied the ultrafast photocarrier dynamics in Zn-doped 3D topological Dirac semimetal Cd3As2 utilizing time-resolved optical pump-terahertz probe spectroscopy. Comparing to the pristine Cd3As2, we found that the relaxation time of the lightly doped alloy is slightly shorter, while that of the heavily doped alloy exhibits a significant prolongation. Pump-fluence- and temperature-dependent transient terahertz spectroscopy indicated that in pristine and lightly doped samples within nontrivial semimetal phase, the photocarrier dynamics are dominated by the cooling of Dirac fermions. In heavily doped alloy, however, the observed longer relaxation process can be attributed to interband electron-hole recombination, which is a result of doping-induced transition into a trivial semiconductor phase. Our investigation highlights that Zn-doping is an effective and flexible scheme for engineering the electronic structure and transient carrier relaxation dynamics in Cd3As2, and offers a control knob for functional switching between diverse optoelectronic devices within the realm of practical applications. Element doping can break the crystal symmetry and realize the topological phase transition in quantum materials, which enables the precise modulation of energy band structure and microscopic dynamical interaction. Herein, we have studied the ultrafast photocarrier dynamics in Zn-doped 3D topological Dirac semimetal Cd3As2 utilizing time-resolved optical pump-terahertz probe spectroscopy. Comparing to the pristine Cd3As2, we found that the relaxation time of the lightly doped alloy is slightly shorter, while that of the heavily doped alloy exhibits a significant prolongation. Pump-fluence- and temperature-dependent transient terahertz spectroscopy indicated that in pristine and lightly doped samples within nontrivial semimetal phase, the photocarrier dynamics are dominated by the cooling of Dirac fermions. In heavily doped alloy, however, the observed longer relaxation process can be attributed to interband electron-hole recombination, which is a result of doping-induced transition into a trivial semiconductor phase. Our investigation highlights that Zn-doping is an effective and flexible scheme for engineering the electronic structure and transient carrier relaxation dynamics in Cd3As2, and offers a control knob for functional switching between diverse optoelectronic devices within the realm of practical applications.
Photonics Research
- Publication Date: Apr. 01, 2025
- Vol. 13, Issue 4, 1028 (2025)
Single-atomic-ensemble dual-wavelength optical frequency standard|On the Cover
Jie Miao, Jingming Chen, Deshui Yu, Qiaohui Yang... and Jingbiao Chen|Show fewer author(s)
We demonstrate a dual-wavelength optical frequency standard based on the dual-optical-transition modulation transfer spectroscopy (DOT-MTS) between different quantum transitions of the rubidium D1 (795 nm) and D2 (780 nm) lines. In a single rubidium atomic ensemble, modulation frequency sidebands from the 780 nm pump beam are simultaneously transferred to both the 780 and 795 nm probe lasers. The DOT-MTS enables the simultaneous stabilization of 780 and 795 nm lasers on a single vapor cell. Both lasers exhibit a frequency instability in the low 10-14 range at 1 s of averaging, as estimated from the residual error signal. A theoretical model is developed based on the V-type atomic level structure to illustrate the dual-wavelength spectroscopy. This approach can be extended to develop a multi-wavelength optical frequency standard within a single atomic ensemble, broadening its applicability in fields such as precision metrology, Rydberg atoms, wavelength standards, optical networks, and beyond. We demonstrate a dual-wavelength optical frequency standard based on the dual-optical-transition modulation transfer spectroscopy (DOT-MTS) between different quantum transitions of the rubidium D1 (795 nm) and D2 (780 nm) lines. In a single rubidium atomic ensemble, modulation frequency sidebands from the 780 nm pump beam are simultaneously transferred to both the 780 and 795 nm probe lasers. The DOT-MTS enables the simultaneous stabilization of 780 and 795 nm lasers on a single vapor cell. Both lasers exhibit a frequency instability in the low 10-14 range at 1 s of averaging, as estimated from the residual error signal. A theoretical model is developed based on the V-type atomic level structure to illustrate the dual-wavelength spectroscopy. This approach can be extended to develop a multi-wavelength optical frequency standard within a single atomic ensemble, broadening its applicability in fields such as precision metrology, Rydberg atoms, wavelength standards, optical networks, and beyond.
Photonics Research
- Publication Date: Feb. 28, 2025
- Vol. 13, Issue 3, 721 (2025)
Differential absorption laser spectroscopy at 8 kHz using precompensated current modulation
A. S. Ashik, Peter John Rodrigo, Henning E. Larsen, and Christian Pedersen
We present a differential laser absorption spectroscopy (DLAS) system operating at 1550 nm for rapid and sensitive gas concentration measurements. A dual-wavelength toggling mechanism is presented, which significantly reduces data processing, hence supporting a high update rate and data robustness against fast-changing environmental conditions. We showcase the ability to toggle between two wavelengths separated by 90 pm in 14 μs and with minimal chirp (∼1 pm), facilitating sensitive DLAS measurements at 8 kHz update rate. This performance is achieved by driving a 1550 nm diode laser with a modified square-wave current pulse, overcoming the thermal time constant limited wavelength-modulation response of the diode laser. A sensitive feedback mechanism ensures excellent long-term wavelength stability better than 1.4 pm peak-to-peak at 8 kHz toggling over 20 h. As a performance test, we measured the volumetric ratio (VMR) of hydrogen cyanide (HCN) gas in a fiber-coupled gas cell with less than 0.2% peak-to-peak variation over 20 h at 40 Hz. A best sensitivity in VMR of 8×10-6 was achieved at 25 ms integration time. The simplicity and high update rate of our system make it well-suited for gas monitoring in dynamic atmospheric and industrial environments. Further, it offers potential utility in applications requiring precise wavelength control, such as injection seeding of pulsed lasers. A simple analytical model is derived, which, in detail, supports the experimental results, hence offering a tool for future design optimization. We present a differential laser absorption spectroscopy (DLAS) system operating at 1550 nm for rapid and sensitive gas concentration measurements. A dual-wavelength toggling mechanism is presented, which significantly reduces data processing, hence supporting a high update rate and data robustness against fast-changing environmental conditions. We showcase the ability to toggle between two wavelengths separated by 90 pm in 14 μs and with minimal chirp (∼1 pm), facilitating sensitive DLAS measurements at 8 kHz update rate. This performance is achieved by driving a 1550 nm diode laser with a modified square-wave current pulse, overcoming the thermal time constant limited wavelength-modulation response of the diode laser. A sensitive feedback mechanism ensures excellent long-term wavelength stability better than 1.4 pm peak-to-peak at 8 kHz toggling over 20 h. As a performance test, we measured the volumetric ratio (VMR) of hydrogen cyanide (HCN) gas in a fiber-coupled gas cell with less than 0.2% peak-to-peak variation over 20 h at 40 Hz. A best sensitivity in VMR of 8×10-6 was achieved at 25 ms integration time. The simplicity and high update rate of our system make it well-suited for gas monitoring in dynamic atmospheric and industrial environments. Further, it offers potential utility in applications requiring precise wavelength control, such as injection seeding of pulsed lasers. A simple analytical model is derived, which, in detail, supports the experimental results, hence offering a tool for future design optimization.
Photonics Research
- Publication Date: Jan. 17, 2025
- Vol. 13, Issue 2, 297 (2025)
Precise spectroscopy of metastable Li+ using the optical Ramsey technique in support of time dilation tests
Peng-Peng Zhou, Shao-Long Chen, Cheng-Gang Qin, Xu-Rui Chang... and Hua Guan|Show fewer author(s)
Time dilation constitutes a crucial aspect of Lorentz invariance within special relativity and undergoes constant scrutiny through numerous Ives-Stilwell-type experiments employing the Doppler effect. In our study, we employed optical Ramsey spectroscopy on a Li+ ion beam to enhance the precision of measuring the intrinsic transition frequency 23S1-23P2 to the level of four parts in 1010 with speed of 0.00035c. Our findings reconciled an existing 2 MHz disparity between collinear and perpendicular laser spectroscopy. Furthermore, in conjunction with previous studies on Li+ ion beams traveling at speeds of 0.064c and 0.338c [Nat. Phys.3, 861 (2007)NPAHAX1745-247310.1038/nphys778; Phys. Rev. Lett.113, 120405 (2014)PRLTAO0031-900710.1103/PhysRevLett.113.120405], we updated the Robertson-Mansouri-Sexl parameter α^ to be (-10.0±9.9)×10-8 and (-2.9±2.0)×10-8, respectively. Time dilation constitutes a crucial aspect of Lorentz invariance within special relativity and undergoes constant scrutiny through numerous Ives-Stilwell-type experiments employing the Doppler effect. In our study, we employed optical Ramsey spectroscopy on a Li+ ion beam to enhance the precision of measuring the intrinsic transition frequency 23S1-23P2 to the level of four parts in 1010 with speed of 0.00035c. Our findings reconciled an existing 2 MHz disparity between collinear and perpendicular laser spectroscopy. Furthermore, in conjunction with previous studies on Li+ ion beams traveling at speeds of 0.064c and 0.338c [Nat. Phys.3, 861 (2007)NPAHAX1745-247310.1038/nphys778; Phys. Rev. Lett.113, 120405 (2014)PRLTAO0031-900710.1103/PhysRevLett.113.120405], we updated the Robertson-Mansouri-Sexl parameter α^ to be (-10.0±9.9)×10-8 and (-2.9±2.0)×10-8, respectively.
Photonics Research
- Publication Date: Dec. 24, 2024
- Vol. 13, Issue 1, 201 (2025)
Hydrogen-enhanced light-induced thermoelastic spectroscopy sensing
Ying He, Yuanzhi Wang, Shunda Qiao, Xiaoming Duan... and Yufei Ma|Show fewer author(s)
A hydrogen (H2)-enhanced light-induced thermoelastic spectroscopy (LITES) sensor is proposed for the first time, to our knowledge, in this paper. The enhancement with H2 significantly reduces the resonance damping of a quartz tuning fork (QTF), leading to a 2.5-fold improvement in the quality factor (Q-factor) to 30,000 without introducing additional noise into the LITES sensor system. Based on the H2-enhancement effect, a self-designed round-head QTF with a low resonance frequency (f0) of 9527 Hz and a fiber coupled multipass cell (MPC) with an optical length of 40 m were utilized to increase the energy accumulation time of QTF and the optical absorption of the target gas, respectively, to demonstrate an ultra-highly sensitive C2H2-LITES sensor. The long-term stability of the H2-enhanced C2H2-LITES sensor was investigated based on Allan deviation analysis. With an optimal integration time of 140 s, the minimum detection limit (MDL) was improved to 290 parts per trillion (ppt). Compared to other reported state-of-the-art C2H2-LITES techniques with similar parameters, this sensor shows a 241-fold improvement in the MDL. This H2-enhancement technique proves to be a highly effective method for achieving a high Q-factor QTF, characterized by its simplicity and efficiency. It offers substantial potential for applications in QTF-based gas sensing. A hydrogen (H2)-enhanced light-induced thermoelastic spectroscopy (LITES) sensor is proposed for the first time, to our knowledge, in this paper. The enhancement with H2 significantly reduces the resonance damping of a quartz tuning fork (QTF), leading to a 2.5-fold improvement in the quality factor (Q-factor) to 30,000 without introducing additional noise into the LITES sensor system. Based on the H2-enhancement effect, a self-designed round-head QTF with a low resonance frequency (f0) of 9527 Hz and a fiber coupled multipass cell (MPC) with an optical length of 40 m were utilized to increase the energy accumulation time of QTF and the optical absorption of the target gas, respectively, to demonstrate an ultra-highly sensitive C2H2-LITES sensor. The long-term stability of the H2-enhanced C2H2-LITES sensor was investigated based on Allan deviation analysis. With an optimal integration time of 140 s, the minimum detection limit (MDL) was improved to 290 parts per trillion (ppt). Compared to other reported state-of-the-art C2H2-LITES techniques with similar parameters, this sensor shows a 241-fold improvement in the MDL. This H2-enhancement technique proves to be a highly effective method for achieving a high Q-factor QTF, characterized by its simplicity and efficiency. It offers substantial potential for applications in QTF-based gas sensing.
Photonics Research
- Publication Date: Dec. 24, 2024
- Vol. 13, Issue 1, 194 (2025)
Enhanced terahertz vibrational absorption spectroscopy using an integrated high-Q resonator
Zhibo Hou, Liao Chen, Rongwu Liu, Chi Zhang... and Xinliang Zhang|Show fewer author(s)
The terahertz (THz) absorption spectrum is a powerful method to identify substances. The improvement focuses on sensitivity and recovery ability. Here, we demonstrate enhanced THz vibrational absorption spectroscopy based on an on-chip THz whispering gallery mode resonator (THz-WGMR). A THz-WGMR with high Q can store energy and enhance the interaction between the THz waves and the target substances to capture the unique absorption fingerprint information. Therefore, it possesses significant sensitivity to identify trace amounts of substances. As a proof of concept, lactose powder and glucose powder are applied to demonstrate the effectiveness of our approach in recovering fingerprint absorption spectroscopy. Compared with a straight waveguide, the high sensitivity of the THz-WGMR is illustrated. The change of the transmissivity caused by the lactose reaches 7.8 dB around 532 GHz for the THz-WGMR, while only 1.4 dB for the straight waveguide, demonstrating the state-of-the-art sensing performance in fingerprint absorption recovery. We believe the proposed integrated THz-WGMR will promote the THz identification of tiny fingerprint substances. The terahertz (THz) absorption spectrum is a powerful method to identify substances. The improvement focuses on sensitivity and recovery ability. Here, we demonstrate enhanced THz vibrational absorption spectroscopy based on an on-chip THz whispering gallery mode resonator (THz-WGMR). A THz-WGMR with high Q can store energy and enhance the interaction between the THz waves and the target substances to capture the unique absorption fingerprint information. Therefore, it possesses significant sensitivity to identify trace amounts of substances. As a proof of concept, lactose powder and glucose powder are applied to demonstrate the effectiveness of our approach in recovering fingerprint absorption spectroscopy. Compared with a straight waveguide, the high sensitivity of the THz-WGMR is illustrated. The change of the transmissivity caused by the lactose reaches 7.8 dB around 532 GHz for the THz-WGMR, while only 1.4 dB for the straight waveguide, demonstrating the state-of-the-art sensing performance in fingerprint absorption recovery. We believe the proposed integrated THz-WGMR will promote the THz identification of tiny fingerprint substances.
Photonics Research
- Publication Date: Jul. 01, 2024
- Vol. 12, Issue 7, 1542 (2024)
Instantaneous preparation of gold-carbon dot nanocomposites for on-site SERS identification of pathogens in diverse interfaces
Yanxian Guo, Ye Liu, Chaocai Luo, Yue Zhang... and Zhiming Liu|Show fewer author(s)
Rapid detection of pathogens present on contaminated surfaces is crucial for food safety and public health due to the high morbidity and mortality of bacterial infections. Herein, a sensitive and efficient method for on-site identification of foodborne pathogens on anisotropic surfaces was developed by using an in situ instantaneously prepared surface-enhanced Raman scattering (SERS) platform. To achieve this, molybdenum-doped gallic acid-derived carbon dots (MCDs) are utilized as the reductant for synthesizing Au@MCDs nanohybrids within just 3 s at ambient temperature. The synergistic effect of the electromagnetic enhancement and charge transfer of Au@MCDs enables excellent SERS performance 10 times stronger than bare Au NPs. The bioassay platform requires less than 5 min to complete the quantitative detection of foodborne pathogens on various microbial-contaminated interfaces with a sensitivity of 10 CFU/mL. This innovative strategy breaks the long-standing limitations of SERS substrates in practical use, such as the time-consuming process, interference of residual surfactants, poor surface stability, and few application scenarios, providing a promising tool for widespread applications in biomedical research and clinical diagnostics. Rapid detection of pathogens present on contaminated surfaces is crucial for food safety and public health due to the high morbidity and mortality of bacterial infections. Herein, a sensitive and efficient method for on-site identification of foodborne pathogens on anisotropic surfaces was developed by using an in situ instantaneously prepared surface-enhanced Raman scattering (SERS) platform. To achieve this, molybdenum-doped gallic acid-derived carbon dots (MCDs) are utilized as the reductant for synthesizing Au@MCDs nanohybrids within just 3 s at ambient temperature. The synergistic effect of the electromagnetic enhancement and charge transfer of Au@MCDs enables excellent SERS performance 10 times stronger than bare Au NPs. The bioassay platform requires less than 5 min to complete the quantitative detection of foodborne pathogens on various microbial-contaminated interfaces with a sensitivity of 10 CFU/mL. This innovative strategy breaks the long-standing limitations of SERS substrates in practical use, such as the time-consuming process, interference of residual surfactants, poor surface stability, and few application scenarios, providing a promising tool for widespread applications in biomedical research and clinical diagnostics.
Photonics Research
- Publication Date: May. 31, 2024
- Vol. 12, Issue 6, 1303 (2024)
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