58.    Atsushi Ishizawa, Kota Kawashima, Rai Kou, Xuejun Xu, Tai Tsuchizawa, Takuma Aihara, Koki Yoshida, Tadashi Nishikawa, Kenichi Hitachi, Guangwei Cong, Noritsugu Yamamoto, Koji Yamada, and Katsuya Oguri, “Direct f-3f self-referencing using an integrated silicon-nitride waveguide,” Optics Express, 30(4), 5265-5273, (February 2022).

57.    H. Mashiko, M. C. Chen, K. Asaga, A. Oshima, I. Katayama, J. Takeda, T. Nishikawa, and K. Oguri, “Spatially resolved spectral phase interferometry with an isolated attosecond pulse,” Opt. Express 28(14) 21025-21034, (July 2020).

56.    Atsushi Ishizawa, Kenya Hitomi, Kazutaka Hara, Kenichi Hitachi, Tadashi Nishikawa, Tetsuomi Sogawa, and Hideki Gotoh, “Simple method for stabilizing an optical frequency comb to an optical reference without an RF signal generator,” OSA Continuum, 2(5), 1706-1712, (April 2019).

55.    K. Hitachi, M. Someya, A. Ishizawa, T. Nishikawa, and H. Gotoh, “Characterization of longitudinal acoustic phonons in InGaAsP multiple quantum wells by asynchronous optical sampling,” Applied Physics Letters 113(20), 201102, (November 2018).

54. Keiko Kato, Yuya Hasegawa, Katsuya Oguri, Takehiko Tawara, Tadashi Nishikawa, and Hideki Gotoh, “Relationship between the Fano asymmetry parameter and time-domain spectra studied by time-resolved measurement of carriers and phonons in p-type Si,” Physical Review B 97(10), 104301, (March  2018).

53.    Atsushi Ishizawa, Takahiro Goto, Rai Kou, Tai Tsuchizawa, Nobuyuki Matsuda,  Kenichi Hitachi, Tadashi Nishikawa, Koji Yamada, Tetsuomi Sogawa, and Hideki Gotoh, “Octave-spanning supercontinuum generation at telecommunications wavelengths in a precisely dispersion- and length-controlled silicon-wire waveguide with a double taper structure,” Applied Physics Letters 111(2), 021105, (July 2017).

52.    K. Hitachi, K. Hara, O. Tadanaga, A. Ishizawa, T. Nishikawa, and H. Gotoh, “Reduced pulse energy for frequency comb offset stabilization with a dual-pitch periodically poled lithium niobate ridge waveguide,” Applied Physics Letters 110(24), 241107, (June 2017).

51.    A. Ishizawa, R. Kou, T. Goto, T. Tsuchizawa, N. Matsuda, K. Hitachi, T. Nishikawa, K. Yamada, T. Sogawa, and H. Gotoh, “Optical nonlinearity enhancement with graphene-decorated silicon waveguides,” Scientific Reports 7, 45520, (April 2017).

50.    A. Ishizawa, T. Nishikawa, T. Goto, K. Hitachi, T. Sogawa, and H. Gotoh,　“Ultralow-phase-noise millimetre-wave signal generator assisted with an electro-optics-modulator-based optical frequency comb,” Scientific Reports 6, 24621, (May 2016).

49.    K. Hitachi, A. Ishizawa, O. Tadanaga, T. Nishikawa, H. Mashiko, T. Sogawa, H. Gotoh, “Frequency stabilization of an Er-doped fiber laser with a collinear 2f-to-3f self-referencing interferometer,” Applied Physics Letters 106 (23), 231106, (June 2015).

48.    K. Oguri, T. Tsunoi, K. Kato, H. Nakano, T. Nishikawa, K. Tateno, T.sogawa, and H. Gotoh, "Dynamical observation of photo-Dember effect on semi-insulating GaAs using femtosecond core-level photoelectron spectroscopy," Appl. Phys. Express 8 (2), 022401 (Feb 2015).

47.    K. Hitachi, A. Ishizawa, T. Nishikawa, M. Asobe, T. Sogawa, "Carrier-envelope offset locking with a 2f-to-3f self-referencing interferometer using a dual-pitch PPLN ridge waveguide," Optics Express 22 (2), 1629-1635 (January 2014).

46.    A. Ishizawa, T. Nishikawa, A. Mizutori, H. Takara, A. Takada, T. Sogawa, and M. Koga, "Phase-noise characteristics of a 25-GHz-spaced optical frequency comb based on a phase- and intensity-modulated laser," Optics Express 21 (24), 29186-29194 (December 2013).

45.    Y. Hayashi, A.S. Pirozhkov, M. Kando, K. Ogura, H. Kotaki, H. Kiriyama, H. Okada, H. Gotoh and T. Nishikawa, "Xe K-shell X-ray generation using conical nozzle and 25 TW laser," Laser and Particle Beams 31 (3), 419-425 (September 2013).

44.    K. Hitachi, A. Ishizawa, T. Nishikawa, M. Asobe, T. Sogawa, "Periodically poled lithium niobate ridge waveguides with high conversion efficiency for 2f-to-3f self-referencing interferometer," Electronics Letters 49 (2), 145-146 (January 2013).

43.    K. Oguri, K. Kato, T. Nishikawa, H. Gotoh, K. Tateno, T. Sogawa, and H. Nakano, "Time-Resolved Surface Photoelectron Spectroscopy of Photoexcited Electron and Hole Dynamics on GaAs Using 92 eV Laser Harmonic Source,"     Jpn. J. Appl. Phys. 51 (7R), 072401-1-6 (July 2012).

42.    A. Ishizawa, T. Nishikawa, A. Mizutori, H. Takara, H. Nakano, T. Sogawa, A. Takada, and M. Koga, "Generation of 120-fs laser pulses at 1-GHz repetition rate derived from continuous wave laser diode," Optics Express 19 (23), 22402-22409 (November 2011).

41.    A. Ishizawa, T. Nishikawa, S. Aozasa, A. Mori, O. Tadanaga, M. Asobe, and H. Nakano, "Efficient carrier-envelope offset locking with a simplified configuration of an f-to-2f interferometer," Japanese Journal of Applied Physics 50 (2), 022502 (February 2011).

40.    H. Nakano, K. Oguri, Y. Okano, and T. Nishikawa, "Dynamics of femtosecond-laser-ablated liquid-aluminum nanoparticles probed by means of spatiotemporally resolved X-ray absorption spectroscopy," Appl. Phys. A 101 (3), 523-531 (November 2010).

39.    A. Ishizawa, T. Nishikawa, A. Mizutori, H. Takara, S. Aozasa, A. Mori, H. Nakano, A. Takada, and M. Koga, "Octave-spanning frequency comb generated by 250-fs pulse train emitted from 25 GHz externally phase-modulated laser diode for carrier-envelope-offset-locking," Electronics Letters 46 (19), 1343-1344 (September 2010).

38.    T. Nishikawa, A. Ozawa, Y. Nishida, M. Asobe, F.-L. Hong, and T. W. Hänsch, "Efficient 494 mW sum-frequency generation of sodium resonance radiation at 589 nm by using a periodically poled Zn:LiNbO₃ ridge waveguide," Optics Express 17 (20), 17792-17800 (September 2009).

37.    K. Oguri, Y. Okano, T. Nishikawa, and H. Nakano, "Dynamics of femtosecond laser ablation studied with time-resolved x-ray absorption fine structure imaging," Phys. Rev. B79 (14), 144106 (April 2009).

36.    A. Ishizawa, T. Nishikawa, S. Aozasa, A. Mori, O. Tadanaga, M. Asobe, and H. Nakano, " Demonstration of carrier envelope offset locking with low pulse energy," Optics Express 16 (7), 4706-4712 (March 2008).

35.    K. Oguri, Y. Okano, T. Nishikawa, and H. Nakano, "Dynamical study of femtosecond-laser-ablated liquid-aluminum nanoparticles using spatiotemporally resolved X-ray-absorption fine-structure spectroscopy," Phys. Rev. Lett. 99 (16), 165003 (Oct 2007).

34.    Y. Okano, K. Oguri, T. Nishikawa, and H. Nakano, "Observation of femtosecond-laser-induced ablation plumes of aluminum using space- and time-resolved soft x-ray absorption spectroscopy," Appl. Phys. Lett. 89 (22), 221502 (Nov 2006).

33.    Y. Okano, K. Oguri, T. Nishikawa, and H. Nakano, "Soft x-ray imaging system for picosecond time-resolved absorption spectroscopy using a femtosecond-laser-plasma source," Rev. Sci. Instrum. 77 (4), 046105 (Apr 2006).

32.    Y. Okano, K. Oguri, T. Nishikawa, and H. Nakano, "Spatial distribution of soft x-ray line emissions from aluminum plasma excited by a pair of femtosecond-laser pulses," J. Appl. Phys. 99 (6), 063302 (Mar 2006).

31.    K. Oguri, Y. Okano, T. Nishikawa, and H. Nakano, "Femtosecond Laser-driven soft x-ray sources for time-resolved spectroscopy," NTT Technical Review 3 (12), 36-44 (Dec 2005).

30.    K. Oguri, Y. Okano, T. Nishikawa, and H. Nakano, "Transient observation of extended x-ray absorption fine structure in laser-melted Si by using femtosecond laser-produced-plasma soft x ray," Appl. Phys. Lett. 87 (1), 011503 (Jul 2005).

29.    T. Nishikawa, H. Nakano, K. Oguri, N. Uesugi, K. Nishio, and H. Masuda, "Nanohole-array size dependence of soft x-ray generation enhancement from femtosecond-laser-produced plasma," J. Appl. Phys. 96 (12), 7537-7543 (Dec 2004).

28.    K. Oguri, T. Nishikawa, T. Ozaki, and H. Nakano, "Sampling measurement of soft-x-ray-pulse shapes by femtosecond sequential ionization of Kr+ in an intense laser field," Opt. Lett. 29 (11), 1279-1281 (Jun 2004).

27.    T. Nishikawa, S. Suzuki, Y. Watanabe, O. Zhou, and H. Nakano, "Efficient water-window X-ray pulse generation from femtosecond-laser-produced plasma by using a carbon nanotube target," Appl. Phys. B-Lasers Opt. 78 (7-8), 885-890 (May 2004).

26.    K. Oguri, T. Ozaki, T. Nishikawa, and H. Nakano, "Femtosecond-resolution measurement of soft-X-ray pulse duration using ultra-fast population increase of singly charged ions induced by optical-field ionization," Appl. Phys. B-Lasers Opt. 78 (2), 157-163 (Jan 2004).

25.    T. Nishikawa, K. Oguri, S. Suzuki, Y. Watanabe, O. Zhou, and H. Nakano, "Enhanced water-window X-ray pulse generation from femtosecond-laser-produced plasma with a carbon nanotube target," Jpn. J. Appl. Phys. Part 2 Express Letters, 42 (8B), L990-L992 (Aug 2003).

24.    J. Q. Lin, H. Nakano, T. Nishikawa, T. Ozaki, and K. Oguri, "Guiding of high-intensity femtosecond laser pulses in evacuated and gas-filled capillaries," Opt. Commun. 221 (4-6), 411-417 (Jun 2003).

23.    K. Oguri, H. Nakano, T. Nishikawa, and N. Uesugi, "Cross-correlation measurement of ultrashort soft x-ray pulse emitted from femtosecond laser-produced plasma using optical field-induced ionization," Appl. Phys. Lett. 79 (27), 4506-4508 (Dec 2001).

22.    T. Nishikawa, H. Nakano, K. Oguri, N. Uesugi, M. Nakao, K. Nishio, and H. Masuda, "Nanocylinder-array structure greatly increases the soft X-ray intensity generated from femtosecond-laser-produced plasma," Appl. Phys. B-Lasers Opt. 73 (2), 185-188 (Aug 2001).

21.    T. Nishikawa, H. Nakano, N. Uesugi, M. Nakao, K. Nishio, and H. Masuda, "X-ray generation from femtosecond-laser-produced plasma on nanostructure-array targets," Journal de physique IV 11 (PR2), 425-428 (Jul 2001).

20.    N. Uesugi, H. Nakano, T. Nishikawa, and P. Lu, "Efficient soft X-ray generation from femtosecond-laser-produced plasma and its application to time resolved spectroscopy," Journal de physique IV 11 (PR2), 397-403 (Jul 2001).

19.    H. Nakano, T. Nishikawa, and N. Uesugi, "Enhanced K-shell x-ray line emissions from aluminum plasma created by a pair of femtosecond laser pulses," Appl. Phys. Lett. 79 (1), 24-26 (Jul 2001).

18.    T. Nishikawa, H. Nakano, N. Uesugi, M. Nakao, and H. Masuda, "Greatly enhanced soft x-ray generation from femtosecond-laser-produced plasma by using a nanohole-alumina target," Appl. Phys. Lett. 75 (26), 4079-4081 (Dec 1999).

17.    P. X. Lu, H. Nakano, T. Nishikawa, and N. Uesugi, "Demonstration of XUV amplification to the ground state in low-charged nitrogen ions," Opt. Commun. 170 (1-3), 71-78 (Oct 1999).

16.    H. Nakano, Y. Goto, P. Lu, T. Nishikawa, and N. Uesugi, "Time-resolved soft x-ray absorption spectroscopy of silicon using femtosecond laser plasma x rays," Appl. Phys. Lett. 75 (16), 2350-2352 (Oct 1999).

15.    T. Nishikawa, H. Nakano, N. Uesugi, and T. Serikawa, "Porous layer effects on soft x-ray radiation emitted from a plasma generated by 130-fs laser pulses irradiating a porous silicon target," Appl. Phys. B-Lasers Opt. 66 (5), 567-570 (May 1998).

14.    H. Nakano, T. Nishikawa, and N. Uesugi, "Strongly enhanced soft x-ray emission at 8 nm from plasma on a neodymium-doped glass surface heated by femtosecond laser pulses," Appl. Phys. Lett. 72 (18), 2208-2210 (May 1998).

13.    T. Nishikawa and N. Uesugi, "Walk-off and pump energy dependence of transverse beam profiles on traveling-wave parametric generation," Opt. Commun. 140 (4-6), 277-280 (Aug 1997).

12.    T. Nishikawa, H. Nakano, H. Ahn, N. Uesugi, and T. Serikawa, "X-ray generation enhancement from a laser-produced plasma with a porous silicon target," Appl. Phys. Lett. 70 (13), 1653-1655 (Mar 1997).

11.    H. Nakano, T. Nishikawa, and N. Uesugi, "Soft x-ray pulse generation from femtosecond laser-produced plasma with reduced debris using a metal-doped glass target," Appl. Phys. Lett. 70 (1), 16-18 (Jan 1997).

10.    H. Nakano, T. Nishikawa, H. Ahn, and N. Uesugi, "Temporal evolution of soft X-ray pulse emitted from aluminum plasma produced by a pair of Ti:sapphire laser pulses," Appl. Phys. Lett. 69 (20), 2992-2994 (Nov 1996).

9.      T. Nishikawa and N. Uesugi, "Pulse narrowing characteristics in traveling-wave optical parametric generation in KTiOPO₄ crystals," J. Appl. Phys. 80 (5), 2589-2594 (Sep 1996).

8.      H. Nakano, T. Nishikawa, H. Ahn, and N. Uesugi, "Effects of an ultrashort prepulse on soft X-ray generation from an aluminum plasma produced by femtosecond Ti:sapphire laser pulses," Appl. Phys. B-Lasers Opt. 63 (2), 107-111 (Aug 1996).

7.      T. Nishikawa and N. Uesugi, "Transverse beam profile characteristics of traveling-wave parametric generation in KTiOPO₄ crystals," Opt. Commun. 124 (5-6), 512-518 (Mar 1996).

6.      H. Ahn, H. Nakano, T. Nishikawa, and N. Uesugi, "Simultaneous measurement of absorption and X-ray emission from preformed plasma generated by ultrashort prepulse," Jpn. J. Appl. Phys. Part 2 - Lett. 35 (2A), L154-L157 (Feb 1996).

5.      T. Nishikawa and N. Uesugi, "Transverse Beam Profiles on Traveling-Wave Optical Parametric Generation in KTiPO₄ Crystals," J. Appl. Phys. 78 (11), 6361-6366 (Dec 1995).

4.      T. Nishikawa and N. Uesugi, "Effects of Walk-Off and Group-Velocity Difference on the Optical Parametric Generation in KTiPO₄ Crystals," J. Appl. Phys. 77 (10), 4941-4947 (May 1995).

3.      T. Nishikawa, N. Uesugi, and J. Yumoto, "Parametric Superfluorescence in KTiPO₄ Crystals Pumped by 1-Ps Pulses," Appl. Phys. Lett. 58 (18), 1943-1945 (May 1991).

2.      T. Nishikawa, N. Uesugi, and H. Ito, "Angle Tuning Characteristics of 2nd-Harmonic Generation in KTiPO₄," Appl. Phys. Lett. 55 (19), 1943-1945 (Nov 1989).

1.      T. Nishikawa and I. Tsutsui, "Consistent and Covariant Commutator Anomalies in Gauge-Theories," Nucl. Phys. B 308 (2-3), 544-560 (Oct 1988).