NANOLAS CEEXC39 Phases

2005 - Phase I

Theoretical studies and material/systems acquisition.

2006 - Phase II and Phase III:

1) A microchip laser system was designed and realized (4 mm diameter, 2 mm thickness), laser diode pumped, capable to generate laser pulses with duration < 500 ps, energy / pulse of 9mJ, 1064 nm wavelength, 1kHz repetition frequency, M²<1.2, standard deviation below 0.3%. Laser parameters obtained are comparable or even superiors to parameters from similar devices realized by important laser companies. This microlaser e is used as an oscillator in the oscillator-amplification laser system for micro-machining.

2) A picosecond laser system with an microchip oscillator,2-passes amplification and frequency converters from IR to green and UV was realized based on original project. This system is capable of laser pulses with pulse duration below 500ps, 10 Hz repetition frequency, energy /pulse in mJ range for 3 different wavelengths: infrared (1064 nm), visible (532 nm), UV (266 nm). This cheap system compared with other products available on the market is used for materials with resolution in 10-300 microns.

3) CPA2101 (Clark- MXR)l aser system was installed. Laser system characteristics are: pulse duration 200fs, 775 nm wavelength, 700mJ energy/pulse, and 2kHz repetition frequency. An opto-mechanic system was developed for this laser system capable of:

• laser pulse energy controlled attenuation;

• sub-micron precision of laser focusing in work area;

• computer controlled of samples movement using a software developed in our group;

• real time observation of the samples/work area with a CCD camera.

This system is capable of materials micro machining in nanometer area as well as direct laser writing of nanostructures in transparent materials at laser wavelength with hundred of nm resolution.

2007 - Phase IV:

1) Picoseconds laser system beam parameters (experimental determined) are in concordance with the theoretical parameters:

- Laser wavelength: 1064-nm; 532-nm; 266-nm

- Energy / pulse: > 12-mJ / 1064-nm; 6-mJ / 532-nm; 1,6-mJ / 266-nm

- Standard deviation (rms): < 1%/ 1064-nm; < 2% /532-nm; < 4% /266-nm

- FWHM pulse duration: ~ 400-ps la 1064-nm

- Intensity profile: Gaussian, ~ TEM_oo

- Quality factor M² : < 1,3

This laser system is capable of high energy pulses in IR, visible and UV, with hundreds of picoseconds pulse-duration and excellent beam propagation/focusing characteristics, which makes it a perfect tool for high resolution laser microprocessing.

2) After the experiments conducted in this phase optimal parameters required for obtaining sub-micron structures by DLW (Direct Laser Writing) method with short laser pulses were determined. Were completed preliminary microprocessing tests using LIFT technique (Laser induced forward transfer). LIFT is a

micro-structuring method recently studied, with some advantages compared to conventional etching techniques because it does not require the use of complex processes such in the case of classical lithography.

Thin films of metal deposited and proposed by the IMT partner were processed: 50 nm Gold films deposited on glass, 100 nm Gold films deposited on silicon, silicon samples, nitrate silica, silver, etc.. By the femtoseconds pulses laser engraving were made structures with sub-microns resolution on metal films and have been identified applications that can be used with the method of laser structuring of materials (metamaterials manufacture, photonic crystals, sensors, etc.).

2008 – Phase V:

1. The picoseconds and femtoseconds laser systems developed/acquired during this project have been used in a series of experimental micro- and nano- processing studies

a) Ps laser

• Ablation studies on Gold and Nitrate Silica films. Experimental Studii de ablatie laser pe filme de aur si nitrura de siliciu. Have been determined experimentally: ablation rate, fluency in the laser focal spot, fluency in ablation threshold.

• Lateral resolution of picosecond laser pulses processing was evaluated: ~ 0,5-μm la 1064-nm; 0,3-μm la 532-nm; 0,23-μm la 266-nm.

b) Fs laser

- Gold Thin films microprocessing: lines samples were formed / characterized, holes networks, CRLH structures (transmission line type 1D, 2D), consisting of inductors and inter digitals capacitors with applications in the wide bandwidth communications (tens / one hundred MHz) .

- LIFT microprocessing: obtaining / characterization of skutterudit structures, with applications in thermal devices for high temperatures

- Laser-induced periodic surface structures (LIPSS) on semiconductor material (ZnO). Obtaining / characterization of periodical structures with 150-500 nm step. Applications: changing the optical properties of surfaces, manufacturing networks diffraction, magnetic recording media texturing, increasing the adherent surface.

- Structures enrollment by nonlinear absorption in transparent media (glass, quartz). Linear structures type wave guide have been formed by modifying the refractive index in the area processed. Applications: the formation of integrated optical components.

2. Disseminating results of the project was achieved through:

• Published papers / participation to International Conferences.

• NANOLAS Workshop, organized on 28 August 2008 at the headquarters INFLPR.

• Project web-page.