The performance of a frequency-modulated continuous-wave light detection and ranging is severely limited by the inherent non-linear chirp when laser diodes with direct frequency modulation are used ...as light sources. The author proposes and demonstrates a new modulation and detection scheme that is immune to non-linear chirp. Sinusoidal frequency modulation and beat phase detection are employed for measuring both the velocity and distance of a target. Relative accuracies below ± 2 mm/s and ± 1 mm are confirmed for velocity and distance measurements, respectively, in the proof-of-principle experiment.
One of the serious limitations in frequency-modulated continuous wave light detection and ranging (FMCW-LiDAR) is the maximum ranging distance as imposed by the coherence of light sources. The author ...proposes and demonstrates a new technique for overcoming the limitation using differential detection scheme between the frequency-fixed carrier and frequency-modulated subcarrier, which are generated from a single laser source. In the proof-of-principle experiment, two reflection points with a 3 m separation are clearly resolved at distances 192.2 m and 1.504 km using a distributed feedback (DFB) laser with the coherence length of 70 m.
The performance of a frequency-modulated continuous wave (FMCW)–light detection and ranging (LiDAR) is severely limited by the inherent non-linear chirp when laser diodes with direct frequency ...modulation are used as light sources. To overcome this limitation, optoelectronic feedback techniques were reported for chirp linearisation. The author propose and demonstrate an alternative technique that is based on regression analysis of FMCW–LiDAR beat signals. It is shown that the waveform of the laser frequency modulation accompanied by the non-linear chirp is analytically expressed in terms of the Fourier series containing both the odd and even harmonics. The analytical expression is utilised in the regression analysis to calculate the unknown distances. A relative accuracy below 1 mm is obtained in the proof-of-principle experiment.
A new technique is proposed and demonstrated for optical fibre chromatic dispersion measurement based on incoherent heterodyne interferometry, which was originally developed for characterising ...optical resonators. The free spectral range of the ring resonators containing a fibre under test is measured as a function of wavelength, from which group delay and chromatic dispersion can be estimated. As compared with the existing methods, the technique has the advantage of simple configuration and procedure.
This paper demonstrates a new type of an optoelectronic oscillator (OEO) that employs a polarization modulator (PolM) for realizing prescaled optical clock recovery and 1 : 2 serial-to-parallel ...conversion of optical data signals. By injecting the 40-Gb/s return-to-zero data signals along with the continuous-wave light, the PolM-OEO generates the 20-GHz clock and two 20-Gb/s data streams simultaneously. The OEO is based on the concept of the regenerative frequency divider, which ensures stable injection-locked operation at 20 GHz even in the absence of subharmonic tones in the input signal. The PolM-OEO is applicable to all-optical modulation format conversion from on-off keying to quadrature phase shift keying by combining it with a cross-phase modulation-based wavelength converter.
Change in Li depth profiles of Ti/NbO/LiPON/LMO/Ti and Ti/LMO/LiPON/NbO/Ti (NbO=Nb2O5, LiPON=Li3.3PO3.8N0.2, LMO = LiMn2O4) batteries prepared on Si substrate on one cycle of charging and discharging ...has been in-situ measured from both Ti/NbO and Ti/LMO sides by ERD (elastic recoil detection analysis) and RBS (Rutherford backscattering spectroscopy) techniques with 9 MeV O+4 ion beam, in order to understand Li transport between NbO to LMO. It is found that on over-charging of the Ti/NbO/LiPON/LMO/Ti battery Li charged in NbO diffuses into top Ti film, but on the Ti/LMO/ LiPON/NbO battery Li does not diffuse into bottom Ti film, but returns back to LMO, reacts with top Ti film and segregates at the Ti surface. The difference in Li transport in both batteries is discussed in terms of the difference in Fermi levels at the interfaces of LMO/Ti and NbO/Ti on the Si substrate.
•Change in Li depth profiles of Ti/NbO/LiPON/LMO/Ti under charging and discharging was measured by ERD technique with 9 MeV O ions.•Li charged once in NbO of Ti/NbO/LiPON/LMO/Ti/prepared on Si substrate is found to diffuse into top Ti by over-biasing.•In Ti/LMO/LiPON/NbO/Ti/Si substrate Li does not diffuse bottom Ti, but returns back to LMO and segregates at top Ti surface.•The difference in Li transport in both systems is discussed in terms of Fermi levels at the interfaces of LMO/Ti and NbO/Ti on Si.
Li Depth profiles at the interfaces of capacitors of Cu/LiPON/Cu and Al/LiPON/Al prepared on buffer Ti layer /SiO2
glass and Au/LATP/Au (LiPON = Li3.3PO3.8N0.2, ...LATP = Li3.1Al0.84Ti1.16Ge1.27P1.73O12) under biasing bottom metal against top metal at earth potential have been in-situ measured by means of elastic recoil detection analysis (ERD) and Rutherford backscattering spectrometry (RBS) techniques. Li has been found to be enriched near the interface with electrode biased negatively, while it is depleted near that biased positively. The Li depth profile in electrolyte has been theoretically calculated, taking into account the transport faction of Li ions, based on hopping diffusion model of Li ions under potential gradient. It is shown that the Li depth profile calculated as a solution of diffusion equation at steady state agrees qualitatively well with the experimental ones and the transport fraction of Li ions in electrolyte is less than unity.
•Li in electrolyte is enriched at the interface with electrode biased at negatively, while it is depleted at that biased positively.•The depth profile corresponds qualitatively well with the calculation on hopping diffusion model under potential gradient.•The transport fraction of Li ions in the electrolyte under the potential gradient is less than unity.
Li depth profiles in Au/LCO/mixed LATP-LAGP/Pt battery (mixed LATP-LAGP (LATP/LAGP) = Li1+X+YAlYTi2−YGeXP3−XO12, LCO = LiCoO2) under discharging by biasing Pt to Au at earth potential, have been ...measured from both Au and Pt surfaces by means of reflection elastic recoil detection (ERD) and Rutherford backscattering spectrometry (RBS) techniques with 9 MeV O4+ ions. Ge and Ti compositions of a mixed LATP-LAGP electrolyte and thickness of LCO were determined from RBS spectrum for the as-prepared specimen, where Y and X in LATP were estimated to be 0.84 and 1.27, respectively. On charging at 2.4 V for 25 min, Li composition in LCO measured from the Au surface by ERD was reduced down to ~0.3 and hereafter on discharging at 0.5 V for 25 min the composition was not enriched, but contrary was further reduced to 0.2. However, by successive discharging at 1.0, 1.5 and 2.2 V for 50 min the composition was enriched. On the other hand, it was found from the Pt surface that Li charged in the electrolyte near Pt by biasing at 2.4 V for 20 min was reduced by discharging at 1.0 V for 20 min. By further discharging for 20 min Li was not reduced, but contrary was enriched. Both anomalous transports of Li under discharging are discussed in terms of diffusion of Li atoms in the counter direction to the biasing which is caused by the transport fraction of Li ions in the electrolyte less than unity.
•Li depth profiles in LCO layer of Au/LCO/mixed LATP-LAGP/Pt battery were uniformly changed over its whole depth on charging/discharging.•Too long loading at charging brought about an anomaly in the battery at which Li was inversely transported from LCO to Pt.•The change in the Li depth profiles on charging/discharging of the battery was reversible and the battery is rechargeable.
Mo/Zr were added to further improve the mechanical properties of W-Y2O3 alloys, thus improving W ductility due to the addition of Y2O3 nanoparticles. Herein, the effects of minor addition of ...elemental Mo/Zr and Fe-ion pre-irradiation on D retention in W-Y2O3 alloys were investigated. The maximal fluence of W-1 wt.%Mo-0.25 wt.%Y2O3 and W-0.1 wt.%Zr-0.25 wt.%Y2O3 samples irradiated with 5-keV-energy D2 ions was 1022 D2/m2, and Fe-ion pre-irradiation was performed at ion fluences of up to 4 × 1018 /m2 at the energy of 1 MeV. For both alloys, the D desorption amount increased with increasing D2-ion irradiation fluence, regardless of Fe-ion pre-irradiation. Compared with W-Y2O3, the overall amount of the D desorption increased for both alloys without Fe-ion pre-irradiation. However, it decreased for both alloys with Fe-ion pre-irradiation, when the D2-ion irradiation fluence was 1022 D2/m2. The addition of Mo/Zr prevented the diffusion of D from the surface to the inside of the sample. Therefore, Fe-ion pre-irradiation had a negligible effect on D desorption in the Mo- or Zr-added W-Y2O3 alloys. Changes in the microstructures of the W alloy owing to the addition of minor elements strongly affected the D desorption. The addition of Mo promoted the formation of dislocation loops during the D2-ion irradiation. In contrast, the addition of Zr refined the Y2O3 particles. These defects served as D trapping sites, thereby weakening the pre-irradiation effect of Fe ions.
A 40-Gb/s optical clock recovery is demonstrated using an injection-locked optoelectronic oscillator (OEO). Injection locking is achieved by directly coupling a return-to-zero optical data stream to ...a photodiode in the OEO. This scheme is advantageous in its simple configuration, wavelength-independent operation, and wide locking range. The pulsewidth and root-mean-square jitter of the recovered clock are 9.8 ps and 283 fs (10 Hz-18.6 MHz), respectively. Furthermore, subharmonic clock recovery from a 160-Gb/s optical time-division-multiplexed data stream is achieved using the same configuration.
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