We report a compact and highly stable 1064-nm electro-optic Q-switched laser operating at the repetition rate of 1 kHz. A composite Nd:YAG crystal was used as the gain media and the cavity length was 105 mm. Under the average pump power of 11 W, the output power achieved 2.404 W with the pulse width of 4.558 ns, corresponding to the maximum peak power of 0.527 MW and the optical-to-optical conversion efficiency of 21.85%. The slope efficiency reached 42.69%. The beam quality in the horizontal (Mx2) and vertical (My2) directions were 1.81 and 1.58, respectively. The pulse timing jitter was less than 1 ns, and the average power fluctuation measured within 30 min was 0.83% (RMS). It is believed that such a compact and highly stable pulsed laser with high repetition rate, high peak power, and good beam quality has great potential in the fields of lidar, etc.
A highly sensitive terahertz parametric up-conversion detector based on KTiOPO4(KTP) crystal pumped by 1064nm laser was demonstrated in this paper. THz wave was generated in KTP crystal with a terahertz parametric oscillator (TPO), which can generate THz wave from 1.17-5.98 THz by varying the phase-matching angle between the pump and Stokes wave inside KTP crystal. THz wave and pump wave were mixed in KTP crystal to generate up-conversion signal based on stimulated parametric scattering. The up-conversion signal was amplified in another two KTP crystals based on non-collinear and collinear phase matching to improve detection sensitivity. Spectrometer and photodiode were used to measure the wavelength and pulse energy of up-conversion signal respectively. The detectable THz frequency range was 4.26-4.50 THz and 4.80-4.92 THz. The minimum detectable energy of 250 pJ was realized with dynamic range of 32 dB at 4.40 THz, and the minimum detectable energy at 4.85 THz was 9.4 pJ with dynamic range of 48 dB. All experiments were carried out under pump threshold conditions of spontaneous parametric noise generation. Compared with LiNbO3 crystal, the parametric up-conversion detection based on KTP crystal can realize high frequency range (>3 THz) THz wave detection, filling in the gaps for high-frequency detection.
We have demonstrated a high energy, widely tunable, long-wave mid-infrared optical parametric oscillator based on BaGa4Se7 crystal (BaGa4Se7-OPO) which was pumped by an economical wavelength of 1.064μm. The BaGa4Se7-OPO was designed as a double pass single resonant oscillator (DP-SRO), with the advantages of low threshold and high output. The output energy and conversion efficiency of BaGa4Se7-OPO with different cavity lengths were studied theoretically and experimentally. The maximum mid-infrared energy of 611μJ/pulse at 11μm was obtained, and the corresponding optical-to-optical conversion efficiency was 1.53%. A wide tuning range of 8.24-13.3μm was achieved by rotating the BaGa4Se7 crystal and it can be well matched with the theoretical calculation.
A novel nested anti-resonant hollow core fiber (NAHF), based on Topas, with low loss and flattened dispersion is proposed for efficient transmission of terahertz wave. Finite element method with an ideally matched layer (PML) boundary condition is used to investigate its guiding properties. A cladding structure of nested anti-resonant elliptical rings is introduced to reduce mode power leakage. The NAHF shows a low confinement loss (< 0.29 cm-1 ) and a small effective material loss (< 0.019 cm-1 ) in the frequency range of 0.9-1.5 THz. An ultra-flatted near zero dispersion profile of ±0.029 ps/THz/cm is obtained within a broad frequency range of 0.6-1.5 THz. Furthermore, optimizing the structure parameters in NAHF, higher core power fraction over 80 %, higher effective mode area of ~10-6 μm2 and the bending loss of 3.05×10-5 cm-1 at the bending radius of 10 cm are also achieved.
We have demonstrated a high-energy and broadly tunable monochromatic terahertz (THz) source via difference frequency generation (DFG) in DAST crystal. The THz frequency is tuned randomly in the range of 0.3-19.6 THz, which is much wider than the THz source based on the inorganic crystal and the photoconductive antenna. The highest energy of 2.53μJ/pulse is obtained at 18.9 THz corresponding to the optical-to-optical conversion efficiency of 1.31×10-4. The THz output spectroscopy is theoretically and experimentally explained by DFG process and Raman spectroscopy. Meanwhile, a phenomenon of blue light from the KTP-OPO with tunable and multiple wavelengths was firstly observed and explained. Based on our THz source, an ultra-wideband THz frequency domain system (THz-FDS) with transmission mode is realized to measure the ultra-wideband THz spectroscopies of typical materials in solid and liquid states, such as Si, SiC, White PE, water, isopropyl myristate, simethicone, atonlein and oleic acid, etc.. Furthermore, we have studied the THz spectral characteristic of biomedical tissue in the ultra-wideband THz frequency range of 0.3-15THz to study the biomedical response in the entire THz frequency range, which contains more abundant spectral information and was rarely focused with the limit of the THz source.
A gain-boosted terahertz-wave parametric generator (TPG) in high frequency tuning range based on MgO-doped nearstoichiometric LiNbO3 (MgO:SLN) crystal has been demonstrated with 1064 nm nanosecond pulsed laser pumping. The pulse-seed is provided by nanosecond singly resonant near-degenerated KTP optical parametric oscillator with the wavelength range of 1068.08 nm to 1084.76 nm. The terahertz tuning range of 0.97 THz to 4.07 THz was achieved. The maximum THz wave output signal was 4285mV at 1.82 THz under the pump energy of 180 mJ and pulse-seed energy of 20.2 mJ. During the frequency range of 1.25 THz to 3.43 THz, the THz output energies were larger than 2000mV. Compared with the maximum THz output energy, the THz energy attenuation factors of 0.55 dB, 1.71 dB and 3.31 dB were realized in pulse-seeded TPG at 2.5 THz, 3.0THz and 3.5THz, respectively. The significantly increasing of THz gain in high frequency range (<2.5 THz) was achieved.
Theoretical simulations were carried out to evaluate the properties of terahertz (THz) generation in β-BaTeMo2O9 (βBTM) crystal by stimulated polariton scattering (SPS) process. The effects of different polariton modes on THz generation were analyzed, from which we determined the optimal crystal design and polarizations of the coupled waves. The dispersion and absorption characteristics of these vibration modes were also given based on the first-principle calculation and correlation Raman spectrum. Finally, the angle phase matching property and THz-wave gain were calculated. Simulation results showed that β-BTM is a kind of potential material for high-power tunable THz generation.
A surface-emitted ring-cavity terahertz (THz) wave parametric oscillator has been demonstrated for high-energy THz output and fast frequency tuning. Through the special optical design with a Galvano optical scanner and four-mirror ring-cavity structure, a maximum THz output of 12.9 μJ/pulse is achieved at 1.359 THz under the pump pulse energy of 172.8 mJ with the repetition rate of 10 Hz. A further research on the performance of the SE ring-cavity TPO has done to explore more characteristics of THz output. The THz pulse instability and the influence of cavity loss has analyzed. Moreover, the pump depletion rate of the ring-cavity configuration is much lower than the conventional surface-emitted terahertz wave parametric oscillator at the same experimental conditions.
A widely tunable, high-energy terahertz wave parametric oscillator based on 1 mol. % MgO-doped near-stoichiometric LiNbO3 crystal has been proposed with 1064 nm nanosecond pulsed laser pumping. The tunable range of 1.16 to 4.64 THz was obtained. Under the pump energy of 150 mJ/pulse, the maximum THz wave output energy of 12.56 μJ was achieved at 1.88 THz, corresponding to the THz wave conversion efficiency of 7.61×10-5 and the photon conversion efficiency of 1.14%, respectively. Moreover, the THz half maximum (FWHM) beam diameters of MgO:SLN TPO measured at 4 cm from the output surface were 7.42 mm and 6.06 mm in the vertical and horizontal directions, respectively.
High-repetition-rate, monochromatic and tunable terahertz (THz) source is demonstrated. We use an orthogonally polarized dual-wavelength intracavity OPO to complete the type-II phase-matched collinear difference-frequency generation in GaSe. A high average-power 2 μm laser with 12 W output power and good beam quality based on an intracavity KTP OPO is experimentally designed. The KTP OPO is intracavity pumped by an acousto-optical Q-switched side-pumped Nd:YAG with the repetition rate of 10 kHz. Two identical KTP crystals were 7 × 8 × 15 mm3 in size, cut at θ = 51.2°, φ = 0°, which were tuned in the x-z plane to achieve type-II phase-matching. The KTP OPO consists of two identical KTP crystals to reduce the walk-off effect and improve the beam overlap area of the output signal and idler waves. The pulse-width of the 2-μm KTP OPO laser is about 11 ns with the linewidth about 0.8 nm. The focused OPO beam is injected into the uncoated GaSe with the length of 8 mm, and the generated THz wave is detected with a 4.2-K Si-bolometer after focusing with a polyethylene lens. The tunable and coherent radiation from 0.2 to 3 THz has been achieved based on the type-II phase-matching DFG when the two pump waves are in the range of 2.1064 - 2.1272 μm and 2.1516 - 2.1304 μm while symmetrically tuning the phase-matching angle of the KTPs. The maximum output THz average power can reach μW-level around 1.48 THz.
A high-power high efficiency picosecond (ps) 355 nm ultraviolet (UV) laser was reported based on the nonlinear optical crystal of type-I phase-matching La2CaB10O19 (LCB) which possesses the characteristic of non-hygroscopicity. The high-power third harmonic generation was successfully achieved from a 1064 nm ps fundamental laser. The maximum output power of 7.81 W of 355 nm UV laser was obtained from 35.2 W 1064 nm ps laser (80 MHz repetition rate, 10 ps pulse width) with optical conversion efficiency of 22.2%. The experimental results show that the LCB crystal has a promising prospect in generating high-power high efficiency UV laser.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.