擬似スーパーコンティニュウム光波を用いたコヒーレントアンチス トークス

⎇ⓥᵴേ
ᡆૃࠬ࡯ࡄ࡯ࠦࡦ࠹ࠖ࠾ࡘ࠙ࡓశᵄࠍ↪޿ߚࠦࡅ࡯࡟ࡦ࠻ࠕࡦ࠴ࠬ
࠻࡯ࠢࠬ࡜ࡑࡦᢔੂ㗼ᓸಽశ
Coherent anti-Stokes
quasi-supercontinuum
Raman
scattering
microscopic
spectroscopy
using
໊Ỉ⋥᮸㧔Naoki KARASAWA㧕
Tel & Fax: 0123-27-6063 E-mail: n-karasa@photon.chitose.ac.jp
Quasi-supercontinuum from a photonic crystal fiber was generated and used as a Stokes pulse in
broadband coherent anti-Stokes Raman scattering (CARS) spectroscopy. The quasi-supercontinuum
was created by modulating optical pulses by an acousto-optic modulator, and the group delays in the
quasi-supercontinuum were compensated for by a pair of high index prisms. By the use of the
quasi-supercontinuum, the CARS measurement time was reduced to be about one eighth compared
with our previous study. With this setup, broadband CARS signals between 900 cm-1 and 3100 cm-1
of a single polystyrene bead sample have been measured successfully.
ࠦࡅ࡯࡟ࡦ࠻ࠕࡦ࠴ࠬ࠻࡯ࠢࠬ࡜ࡑࡦᢔੂ㧔CARS㧕ಽశߪ⿥⍴శࡄ࡞ࠬ࡟࡯ࠩ࡯ࠍశḮ
ߣߒߡ↪޿‫ࡊࡦࡐޔ‬శߣߘࠇߣᵄ㐳߇⇣ߥࠆࠬ࠻࡯ࠢࠬశࠍ↢૕ߥߤߩ⹜ᢱߦ㓸శߒ‫ߘޔ‬
ߩߣ߈⹜ᢱߩಽሶᝄേߦ౒㡆⊛ߦ⊒↢ߔࠆࠕࡦ
࠴ࠬ࠻࡯ࠢࠬశᵄࠍಽశߔࠆᣇᴺߢ޽ࠆ‫ޕ‬ᚒ‫ޘ‬
ߪࡈࠜ࠻࠾࠶ࠢ⚿᥏ࡈࠔࠗࡃ࡯㧔PCF㧕ߦ࠴࠲
ࡦࠨࡈࠔࠗࠕ࡟࡯ࠩ࡯߆ࠄߩశࡄ࡞ࠬࠍዉᵄߒ‫ޔ‬
⊒↢ߔࠆၮᧄ࠰࡝࠻ࡦࡄ࡞ࠬࠍࠬ࠻࡯ࠢࠬశߣ
ߒߡ↪޿ࠆᐢᏪၞ CARS 㗼ᓸಽశశቇ♽ߩ⹜૞
ࠍⴕߞߡ߈ߚ‫⎇ᧄޕ‬ⓥߢߪᓥ᧪ߩᚻᴺߦᲧߴ‫ޔ‬
ࠃࠅᒝᐲ߇ᐔမߢ᷹ቯᤨ㑆ߩ⍴❗߇ᦼᓙߐࠇࠆ
ᡆૃࠬ࡯ࡄ࡯ࠦࡦ࠹ࠖ࠾ࡘ࠙ࡓశࠍ↪޿ߚᐢᏪ
ၞ CARS ಽశታ㛎ࠍⴕߞߚ‫ޕ‬
Fig
1
The
spectrum
of
quasi-supercontinuum (black curve) and
the spectrum of a single fundamental
soliton pulse (dashed curve).
ታ㛎ߦ߅޿ߡߪ㖸㗀శቇ⚛ሶߦࠃࠅ PCF ߦ౉
኿ߔࠆశᵄߩᒝᐲࠍ๟ᵄᢙ 500 KHz ߢᄌ⺞ߒ‫ޔ‬
ᡆૃࠬ࡯ࡄ࡯ࠦࡦ࠹ࠖ࠾ࡘ࠙ࡓࠍ⊒↢ߐߖߚ‫ޕ‬
Fig㧝ߦߘߩࠬࡍࠢ࠻࡞ࠍ␜ߔ‫ߚࠇߐ↢⊒ޕ‬ᡆ
ૃࠬ࡯ࡄ࡯ࠦࡦ࠹ࠖ࠾ࡘ࠙ࡓߪᵄ㐳ߣㆃᑧᤨ
㑆ߩ⇣ߥࠆၮᧄ࠰࡝࠻ࡦࡄ࡞ࠬߩ㓸߹ࠅߢ޽
ࠆ߇‫߈ߣߩߎޔ‬ㆃᑧᤨ㑆ߦߟ޿ߡߪ㜞ዮ᛬₸ࠟ
࡜ࠬࡊ࡝࠭ࡓኻࠍ PCF ߩ಴ജㇱߦᝌ౉ߒߘߩ
⵬ఘࠍⴕ޿‫ࠅࠃߦࠇߎޔ‬ᐢᏪၞߢାภ߇㜞ᒝᐲ
ߥ CARS ⸘᷹ࠍⴕ߁ߎߣ߇น⢻ߣߥߞߚ‫ޕ‬Fig 2
ߦߎࠇࠄࠍ↪޿ߡᓧࠄࠇߚන৻ࡐ࡝ࠬ࠴࡟ࡦ⃿
㧔⋥ᓘ 6Pm㧕ߩ CARS ାภࠍ␜ߔ‫੹ޕ‬࿁ߩᡆૃ
Fig 2 The CARS signal of a single
polystyrene bead (black curve). The
spontaneous Raman shifts are shown by
dashed lines.
ࠬ࡯ࡄ࡯ࠦࡦ࠹ࠖ࠾ࡘ࠙ࡓࠍ↪޿ߚᣇᴺߦࠃࠅ‫ޔ‬
ᓥ᧪ߩ⚂ 8 ಽߩ㧝ߩ 0.3 ⑽ߩ᷹ቯᤨ㑆ߢ 900 cm1 ߆ࠄ 3100 cm1 ߩᐢᏪၞߩ CARS ାภ߇᣿
⍎ߦ᷹ⷰน⢻ߥߎߣ߇ࠊ߆ߞߚ‫ޕ‬
㧙 101 㧙
⎇ⓥᵴേ
ࡈࠜ࠻࠾࠶ࠢ⚿᥏ࡈࠔࠗࡃ࡯߆ࠄߩ㜞ᰴࡕ࡯࠼ബ⿠ߦࠃࠆಽᢔᵄߩ
⊒↢
Generation of dispersive waves from a photonic crystal fiber by higher-order mode
excitation
໊Ỉ⋥᮸㧔Naoki KARASAWA㧕
Tel & Fax: 0123-27-6063 E-mail: n-karasa@photon.chitose.ac.jp
Dispersive waves were generated from a photonic crystal fiber by higher-order mode excitation and
the dependence of their wavelengths on polarization was measured. The dispersion properties of
various spatial modes with different symmetry numbers were calculated theoretically and four
combinations of linearly-polarizing higher-order modes were identified. The phase-matching
conditions of dispersive waves for higher-order modes were calculated and it was found that the
wavelengths of dispersive waves with identical spatial modes depended on polarization directions.
The dependence measured experimentally agreed well with results obtained by theoretical
calculations.
ࡈࠜ࠻࠾࠶ࠢ⚿᥏ࡈࠔࠗࡃ࡯㧔PCF㧕ߦ⿥⍴శࡄ࡞ࠬࠍዉᵄߔࠆߣ⿥ᐢᏪၞశᵄࠍ⊒↢ߢ
߈ࠆߎߣ߇⷗಴ߐࠇ‫ޔ‬᭽‫ߥޘ‬ᔕ↪ߦ↪޿ࠄࠇߡ޿ࠆ‫⿥ޕ‬ᐢᏪၞశᵄߩ⊒↢ߪ PCF ߩಽᢔ߇
ബ⿠ᵄ㐳ߢ⇣Ᏹಽᢔߢ޽ࠅ‫ޔ‬㜞ᰴ࠰࡝࠻ࡦߩવ៝ߣߘߩၮᧄ࠰࡝࠻ࡦ߳ߩಽⵚ෸߮ၮᧄ࠰
࡝࠻ࡦߣ૏⋧ᢛวߩߣࠇߚಽᢔᵄߩ⊒↢ߢ⺑᣿ߐࠇࠆ‫⎇ᧄޕ‬ⓥߦ߅޿ߡߪ㜞ᰴࡕ࡯࠼વ៝
ߦ߅޿ߡ߽ಽᢔᵄ߇⊒↢ߒ‫ߩߘޔ‬ᵄ㐳߇஍శᣇะߦଐሽߔࠆߎߣࠍ⷗಴ߒߚ‫ޕ‬
ᧄታ㛎ߢߪ⋥ᓘ߇ 1.57 Pm ߩⓨሹ߇ 6 ⷺᩰሶ⁁ߦࡇ࠶࠴߇ 2.27 Pm ߢ 5 ࡝ࡦࠣᒻᚑߐࠇߚ
PCF ࠍ↪޿ߚ‫ߩࠄ߆࡯ࠩ࡯࡟ࠕࠗࠔࡈࠨࡦ࠲࠴ߦࠇߎޕ‬ᵄ㐳 810 nm‫ࠬ࡞ࡄޔ‬᏷ 50 fs ߩశࡄ
࡞ࠬࠍ౉኿ߐߖߚ‫ޕ‬ၮᧄࡕ࡯࠼વ៝ߢߪಽᢔᵄߩ⊒↢ߪ⷗ࠄࠇߥ߆ߞߚ߇‫ޔ‬㜞ᰴࡕ࡯࠼વ
៝ߢߪนⷞశߩ㗔ၞߦಽᢔᵄߩ⊒↢߇⷗ࠄࠇ‫ߩߘޔ‬ᵄ㐳ߪ஍శᣇะߦଐሽߒߚ‫ޕ‬Fig㧝ߦߘ
ߩࠬࡍࠢ࠻࡞ࠍ␜ߔ‫ޕ‬ℂ⺰⸘▚ߦࠃࠅ㜞ᰴࡕ࡯࠼ߪⓨ㑆⊛ኻ⒓ᕈߩ⇣ߥࠆ㧠ߟߩࡕ࡯࠼㧔p1‫ޔ‬
p2‫ޔ‬p5‫ޔ‬p6㧕ߩ✢ᒻ⚿วߢ⴫ࠊߐࠇࠆߎߣ߇ࠊ߆ߞߚ‫ޕ‬ၮᧄ࠰࡝࠻ࡦࡄ࡞ࠬߣ૏⋧ᢛว߇
ߣࠇࠆߚ߼ߩಽᢔᵄߩᵄ㐳ࠍℂ⺰⊛ߦ⸘▚ߒߚ߽ߩࠍ Fig 2 ߦ␜ߔ‫ࠅࠃࠇߎޕ‬ห৻ߩⓨ㑆ࡕ
࡯࠼ࠍᜬߟ㜞ᰴࡕ࡯࠼ߦ߅޿ߡ‫ޔ‬஍శᣇะ߇⇣ߥࠆߣಽᢔᵄߩᵄ㐳⇣ߥࠆߎߣ߇੍᷹ߐࠇ‫ޔ‬
ታ㛎ߢߩ⚿ᨐ߇⺑᣿ߐࠇߚ‫ߦ߁ࠃߩߎޕ‬ಽᢔᵄߩᵄ㐳߇஍శᣇะߢ೙ᓮߢ߈ࠆߎߣ߆ࠄ‫ޔ‬
㜞ㅦశᄌ⺞╬߳ߩᔕ↪߇⠨߃ࠄࠇࠆ‫ޕ‬
Fig 2 The dispersive wave wavelength versus
pump wavelength for higher-order modes
Fig 1 The spectra of dispersive waves and
with different symmetry numbers.
spatial
modes.
Arrows
indicate
polarization directions.
ෳ⠨ᢥ₂㧦N. Karasawa and K. Tada, Opt. Express, 18, 5338 (2010).
㧙 102 㧙