Laser structuring

Mold plastic body Mold plastic body 

Laser structuring of photoresist Galvanically build etch resist 

Galvanic copper and surface finishing Laser structuring of etch resist 

Etch away photoresist and base metallization Etch away copper 

FIGURE 3.2 Process steps in additive, semiadditive, and subtractive laser structuring as in [48] 

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R.J. Nelson and N.K. Dutta, Review of InGaAsP/InP Laser Structures and Comparison of Their Performance... 

The complete manufacturing is divided into a number of production modules, e.g. for coating, laser structuring and reactor mass-producing. This facilitates the identification of possible defects in the production line and also permits parallel development. 

The first of three modules is the coating module, which is followed by the laser structuring and reactor folding modules. 

Figure4.110 Principle of laser structuring and photograph of the laser module showing the two axes-driven laser head [109],...

As the foil shaping by pistons demands the repeated stopping of the conveyance for the period of the shaping, the laser structuring, foil shaping and the coating will also have to be controlled and aligned to assure a common frequency for these steps. 

For the period of the foil shaping, the coating knife must be positioned on a section of the foil which is not structured. This prevents the slurry from delivering an undefined coat thickness and helps to seal the jet exit This is one of the reasons for the existence of the laser structuring module as this foil section will be thinned by the laser after the coating step to create a predefined joint for the subsequent folding process. 

A double-sided U-shaped foil, as shown in Figure 4.113, permits the execution of an exothermic reaction on the coated laser-structured upper side of the foil and... 

Laser structured folding area (surface lower than channel floor to define folding position)... 

C5.1 InGaN/GaN/AlGaN-based laser diodes C5.2 Optically pumped lasing and current injection lasing in GaN-based laser structures... 

C EXPERIMENTAL DATA ON OPTICAL GAIN IN GaN-BASED LASER STRUCTURES... 

Both injection-type and optically pumped nitride-based semiconductor laser structures exhibit fairly high threshold pump levels compared to other III-V or II-VI semiconductors. This is fundamentally due to the specific band structure of the nitrides, i.e. the extremely large effective masses of both electrons and holes. The carrier densities needed to achieve transparency are of the order 2 x 1019 cm 3. 

FIGURE 4 (a) Hole and (b) electron density distribution through the laser structure. Both distributions are inhomogeneous, increasing toward the p-sidc. 

Fig. 2 presents the gain spectrum for the laser structure with Xi = 1.8 nm obtained using the method of variation of exciting stripe length. The stripe length L was 50 pm for these measurements, the pumping power density was - 47.5 GW/cm. It is seen that amplification occurs in a wide interval of 80 nm and the gain value reaches 85 cm. ... 

New kinds of dilute-nitride type-II InAsN/GaSb laser diodes on InAs substrate with "W" or "M" design are theoretically investigated. For these laser diodes, designed to qjerate at 3.3 im at room temperature, the total threshold current densities are calculated. Under the hypothesis of a total loss coefficient a = 50 cm", these multiquantum well laser structures present a calculated threshold current density J lower than 1.1 kA/cm. ... 

In this communication, dilute-nitride type-II "W" and "M" InAsN/GaSb laser diodes on InAs substrate are theoretically investigated. We compare the performances of each laser structures in terms of modal gain and threshold current densities and we discuss their possibilities to operate at RT. 

Figure 1. Conduction and valence band profiles of the dilute-N W" InAsN/GaSb/InAsN and "M" GaSb/InAsN/GaSb laser structures on InAs substrate. On the upper part, fundamental electron (ei) and heavy hole (hhi) presence probability densities are reported. Tbe ei-hhi optical transitions are expected at 3.3 pm at RT.

Figure 2. Dilute-N "M" laser structure RT Gain Figure 3. Maximum gain Gmax vs carrier spectra (TE mode) for different carrier injection concentration N2D (cm ) calculated at 300 K densities N2D (xlO cm ). forthe W" and "M" laser structures.

To evaluate the total current density Jtotai for laser structures, we used the relation J,otai = q Lz (A N3D+B N3d +C Nsd ), where q is the electron charge, Lz is the total thickness of the recombination region equal to Np x Lg, A is the non-radiative recombination coefficient, B is the spontaneous radiative recombination coefficient, and C is the non-radiative Auger coefficient. Typically A=10 s, while coefficients B and C can be deduced from RT calculations of the radiative and Auger recombination rate, respectively [5]. Fig. 5 reports the modal gain G od as a function of Jtot at RT. For a total loss coefficient a = 50 cm", the "W" dilute-N laser structure can operate with a threshold current density Jth equal to 750 A/cm while the predicted RT J,h value for the "M" laser structure is around 1000 A/cm. ... 

Figure 4. Calculated TE polarized modal gain Figure 5. Calculated TE polarized modal gain Gmod versus carrier concentration Nso (cm ) for Gmod versus total current density J,ot for the the dilute-N " W" and "M" laser structures at RT. dilute-N "W" and "M" laser structures at RT.

Spectroscopic properties of isolated human epidermis were measured with dye lasers. Structures in transmission or absorption spectra could be resolved, which were not found with usual spectrophotometers 92). The optical behaviour of isolated skin treated with photosensitizing dyes was also investigated with tunable lasers e.g. changes in transmission after irradiation with different laser wavelengths were detected 92,93), Such dyes are used in photochemotherapy of dermatosis and tumors. 

Introducing a functional ester group that enables selective photocrosslinking without destruction of the polymer backbone can improve the stability of the polymers without changing the sensitivity to direct laser structur-... 

Fig. 82 SEM pictures of the CM polymer after cross-linking. Top after wet development in CHC13 middle structuring of the cross-linked and wet developed polymer (from top SEM) (1 pulse with 7.9 J cm 2 at 308 nm) bottom inverse processing, i.e., first laser structuring, then cross-linking and wet development. REPRINTED WITH PERMISSION OF [Ref. 120], COPYRIGHT (2000) Wiley-VCH Verlag GmbH...

To test whether there is a preferential order of processing steps, i.e., first negative development and then positive laser structuring or vice versa, a polymer film was first structured with the laser, then cross-linked and developed in CHC13. The microstructure (Fig. 82, bottom) reveals the same quality (as far as we can judge from SEM pictures) as the structures obtained for the experiments with the opposite sequence. Of course volume shrinkage upon cross-linking is expected, but was not determined in this study, where only the feasibility of the +/- concept was the aim. 

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