Femtosecond laser micromachining in transparent materials

Femtosecond laser micromachiningin transparent materialsBragg Gratings, Photosensitivity and Polingin Glass Waveguides Topical MeetingKarlsruhe, Germany, 23 June 2010

Rafael GattassLoren CeramiTina ShihMasanao Kamata

and also....Iva MaxwellSan ChungEli GlezerChris SchafferNozomi NishimuraJonathan AshcomJeremy HwangNan ShenDr. André BrodeurDr. Sanjoy KumarDr. Limin TongDr. Prissana ThamboonProf. Igor Khruschev (Aston University)Prof. Denise Krol (UC Davis)Dr. Yossi Chay (Sagitta, Inc.)Dr. S.K. Sundaram (PNNL)Prof. Minoru Obara (Keio University)Prof. Don Ingber (Harvard Medical School)Prof. Aravi Samuel (Harvard)

My messagefs micromachining: great technique for manipulating matter

Introduction

Introductionfocus laser beam inside material100 fstransparentmaterialobjectiveOpt. Lett. 21, 2023 (1996)

Introduction

Introductionphoton energy < bandgapnonlinear interaction

Introductionnonlinear interaction provides bulk confinement

Introductionnonlinear interaction provides bulk confinementlinearabsorptionnonlinearabsorption

Femtosecond micromachiningSome applications:• data storage• waveguides• microfluidics

Outline• femtosecond micromachining• low-energy machining• applications

Femtosecond micromachiningDark-field scatteringobjectivesample

Femtosecond micromachiningblock probe beam…detectorprobeobjectivesample

Femtosecond micromachining… bring in pump beam…pumpdetectorprobeobjectivesample

Femtosecond micromachining… damage scatters probe beampumpdetectorprobeobjectivesample

Femtosecond micromachiningscattered signal3signal (a.u.)21fused silica0.1 µJ0–0.2 0 0.2 0.4 0.6 0.8time (µs)

Femtosecond micromachiningscattered signal3signal (a.u.)21fused silica1.0 µJ0–0.2 0 0.2 0.4 0.6 0.8time (µs)

Femtosecond micromachiningscattered signal3signal (a.u.)21plasmafused silica1.0 µJ0–0.2 0 0.2 0.4 0.6 0.8time (µs)

Femtosecond micromachiningscattered signal3signal (a.u.)21fused silica1.0 µJpermanentchange0–0.2 0 0.2 0.4 0.6 0.8time (µs)

Femtosecond micromachiningscattered signal3signal (a.u.)21thermaltransientfused silica1.0 µJ0–0.2 0 0.2 0.4 0.6 0.8time (µs)

Femtosecond micromachiningvary numerical aperture200threshold (nJ)10000 0.5 1.0 1.5numerical aperture

Femtosecond micromachiningvary numerical intensity aperturethreshold: threshold (nJ)200100spot size determined bynumerical aperture: 00 0.5 1.0 1.5numerical aperture

Femtosecond micromachiningfit gives threshold intensity: I th= 2.5 x 10 17 W/m 2200threshold (nJ)10000 0.5 1.0 1.5numerical aperture

Femtosecond micromachiningvary material…threshold intensity (10 17 W/m 2 )4.54.03.53.02.52.00211SF11BK7FSbandgap (eV)CaF 2LiF2 4 6 8 10 12

Femtosecond micromachining…threshold varies with band gap (but not much!)threshold intensity (10 17 W/m 2 )4.54.03.53.02.52.00211SF11BK7FSbandgap (eV)CaF 2LiF2 4 6 8 10 12

Femtosecond micromachiningwhat prevents damage at low NA?

Femtosecond micromachiningCompeting nonlinear effects:• multiphoton absorption• supercontinuum generation• self-focusing

Femtosecond micromachiningwhy the difference?high NAlow NA

Femtosecond micromachiningvery different confocal length/interaction lengthhigh NAlow NA

Femtosecond micromachininghigh NA: interaction length too short for self-focusing

Femtosecond micromachiningthreshold for supercontinuum generation1.0threshold energy (µJ)0.80.60.40.200.01 0.1 1numerical aperture

Femtosecond micromachiningthreshold for damage1.0threshold energy (µJ)0.80.60.40.200.01 0.1 1numerical aperture

Femtosecond micromachiningPoints to keep in mind:• threshold critically dependent on NA• surprisingly little material dependence• avalanche ionization important

Outline• femtosecond micromachining• low-energy machining• applications

Low-energy machiningthreshold decreases with increasing numerical aperture200threshold (nJ)10000 0.5 1.0 1.5numerical aperture

Low-energy machiningless than 10 nJ at high numerical aperture!200threshold (nJ)10000 0.5 1.0 1.5numerical aperture

Low-energy machiningamplified laser: 1 kHz, 1 mJ1 ms100 fsheat diffusion time: t diff ≈ 1 µs

Low-energy machininglong cavity oscillator: 25 MHz, 25 nJ40 ns30 fsheat diffusion time: t diff ≈ 1 µs

Low-energy machining50 µm

Low-energy machiningHigh repetition-rate micromachining:• structural changes exceed focal volume• spherical structures• density change caused by melting

Low-energy machiningamplified laseroscillator1 ms40 nsrepetitivecumulative

Low-energy machiningamplified laseroscillator repetitivecumulative

Low-energy machiningthe longer the irradiation…10 2 50 µm

Low-energy machiningthe longer the irradiation…10 2 10 350 µm

Low-energy machiningthe longer the irradiation…10 2 10 3 10 450 µm

Low-energy machiningthe longer the irradiation…10 2 10 3 10 4 10 550 µm… the larger the radius

Low-energy machining12radius (µm)84010 110 210 3number of shots10 410 5

Low-energy machiningrepetition-rate dependencenumber of pulses10 210 310 410 5 As 2 S 3 , 100 fs, 7 nJ0.11 10repetition rate (MHz)

Low-energy machiningrepetition-rate dependencenumber of pulses10 210 310 410 5 As 2 S 3 , 100 fs, 7 nJ0.11 10repetition rate (MHz)

Low-energy machiningrepetition-rate dependencenumber of pulses10 210 310 410 5 As 2 S 3 , 100 fs, 7 nJ0.11 10repetition rate (MHz)

Low-energy machiningrepetition-rate dependence8radius (µm)64N10 510 410 310 2200.1 1 10 100repetition rate (MHz)As 2 S 3 , 100 fs, 7 nJ

Low-energy machiningat high-rep rate: internal “point-source of heat”

Outline• femtosecond micromachining• low-energy machining• applications

Low-energy machiningwaveguide micromachiningOpt. Lett. 26, 93 (2001)

Low-energy machiningwaveguide micromachiningOpt. Lett. 26, 93 (2001)

Low-energy machiningstructures guide lightOpt. Lett. 26, 93 (2001)

Low-energy machiningnear-field profiles10 mm/s–20 0 20x (µm)–20 0 20y (µm)20 mm/s–20 0 20x (µm)–20 0 20y (µm)Sagitta, Inc.

Low-energy machiningindex profile at 2.5 mm/s1.5181.516n1.5141.512–20 –10 0 10 20x (µm)Sagitta, Inc.

Low-energy machiningindex profile at 10 mm/s1.5181.516n1.5141.512–20 –10 0 10 20x (µm)Sagitta, Inc.

Applicationscurved waveguides

Applicationscurved waveguides

Applicationscurved waveguides

Applicationscurved waveguides

Applicationscurved waveguides

Applicationsphotonic fabrication techniquesfs micromachiningotherloss (dB/cm) < 3 0.1–3bending radius 36 mm 30–40 mmDn 2 x 10 –3 10 –4 – 0.53D integration Y N

Applicationsphotonic devices3D splitterBragg gratingdemultiplexerλ 1λ 2λ 3λ 4λ 5amplifier interferometer

Applicationsall-optical sensorsubstrateAppl. Phys. Lett. 87, 051106 (2005)

Applicationsall-optical sensorsubstrateAppl. Phys. Lett. 87, 051106 (2005)

Applicationsall-optical sensorsuspended beamsubstrateAppl. Phys. Lett. 87, 051106 (2005)

Applicationsall-optical sensorglasssuspended beamsubstrateAppl. Phys. Lett. 87, 051106 (2005)

Applicationsall-optical sensorfs laserglasslenssuspended beamsubstrateAppl. Phys. Lett. 87, 051106 (2005)

Applicationsall-optical sensorglasswaveguidesuspended beamsubstrateAppl. Phys. Lett. 87, 051106 (2005)

Applicationsall-optical sensorglasswaveguidesuspended beamsubstrateAppl. Phys. Lett. 87, 051106 (2005)

Applicationsall-optical sensorglasswaveguidefibersuspended beamsubstrateAppl. Phys. Lett. 87, 051106 (2005)

Appl. Phys. Lett. 87, 051106 (2005)Applications

Applicationssensor gap20 µmAppl. Phys. Lett. 87, 051106 (2005)

Applicationscalibration15(dB)10loss50–15 –10 –5 0 5 10 15lateral offset (µm)Appl. Phys. Lett. 87, 051106 (2005)

Applicationssensor response to 100 Hz acoustic wave31.0log P (a.u.)21output (a.u.)0.500 50 100time (ms)00 100 200 300 400 500frequency (Hz)Appl. Phys. Lett. 87, 051106 (2005)

Applicationsideal tool for ablating (living) tissue

Applications• standard biochemical tools: species selective• fs laser “nanosurgery”: site specific

ApplicationsQ: can we probe the dynamics of the cytoskeleton?

Applicationsactin fiber network of a live cell10 µm

Applicationscut a single fiber bundle10 µm

Applicationscut a single fiber bundle10 µm

Applicationsgap widens with time10 µmt = 10 s

Applicationsdynamics provides information on in vivo mechanics10 µm

Summarygreat tool for• “wiring light”• micromanipulating the machinery of life

Summary• important parameters: focusing, energy, repetition rate• nearly material independent• two regimes: low and high repetition rate• high-repetition rate (thermal) machining fast, convenient

Funding:Army Research OfficeNational Science Foundationfor a copy of this presentation:http://mazur-www.harvard.edu

Funding:Army Research OfficeNational Science Foundationfor a copy of this presentation:http://mazur-www.harvard.edu