DE102010024266A1 - Micro-optical interferometer i.e. optical delay interferometer, for e.g. refraction index measurement, has monolithic molded bodies with optical boundary surfaces having entry point, beam splitter, reflection point and interference point - Google Patents

Abstract

The interferometer has open jet-optical components arranged such that incident light is guided by open jet-optical total reflection. The components have a set of monolithic molded bodies (2) provided with optical boundary surfaces. The boundary surfaces have an entry point (1), a beam splitter (3), a reflection point (6) and an interference point (7). The molded bodies are made of transparent material e.g. glass and polymeric material, that is suitable for wavelength of the incident light. The boundary surfaces have optical limit angles for splitting the incident light.

Description

The present invention relates to a micro-optic interferometer having free-bright optical components of a monolithic molded body comprising optical interfaces.

Micro-optic interferometers are used for versatile precision measurements. Frequent fields of application are refractive index measurements, length measurements and spectroscopic measurements. For interferometry, at least two light beams return separate optical paths and are brought together again at an interference point. The different optical paths then lead to an interference pattern being produced at the interference point, which is evaluated.

Known interferometers are based on glass optical components, as can be seen in the general state of the art.

The DE 10 2005 021 783 A1 discloses such a glass-based interferometer. Also known are hybid interferometers comprising the glass components. A hybrid arrangement in LIGA technology with glass components is for example the C. Solf, Development of Miniaturized Fourier Transform Spectrometers and Their Production with the LIGA Method, Dissertation, University of Karlsruhe, (2004) refer to.

In addition, hybrid constructed interferometers based on silicon are known, as in US Pat O. Manzardo et. al. "Miniaturized lamellar grating interferometer based on silicon technology", Opt. Letters, Vol. 29 1437-1439, (2002) is disclosed.

In these hybrid interferometers, optical elements are interconnected, with the most common form of the compound being gluing. In the compounds, however, it comes to internal reflections, they adversely affect the particular application.

For the glass components described above optical coatings are needed, the production of which is complicated and expensive. In addition, hybrid systems incur costs and expenses for the assembly and adjustment of the components. Thermal and mechanical stresses on the components or component assembly can also lead to misalignments that can adversely affect the reliability of the result.

Based on this, the object of the invention is to provide an interferometer which avoids the limitations and disadvantages listed. In particular, an interferometer is to be specified that can be operated without expensive and expensive optical components to be adjusted.

This object is achieved with a micro-optical interferometer with the features of claim 1. The dependent claims indicate advantageous embodiments of the invention.

To solve the problem, an interferometer is proposed, the free-beam components of which comprise a monolithic shaped body which has optical interfaces. These optical interfaces are generated by the geometric shape of the molding over optical critical angle. The light guide within the monolithic shaped body is effected by total reflection, by appropriate choice of the optical angle. In addition, the monolithic shaped body comprises other critical angles, which cause a beam splitting or a polarization separation of the incident light at the optical interface.

The optical interfaces for beam splitting and polarization separation are formed by critical angles. An example of such critical angles is the Brewster angle. This indicates the angle at which, in the case of incident unpolarized light, only the components polarized perpendicular to the plane of incidence are reflected. Due to the geometry of the monolithic molded body, a plurality of critical angles can be arranged such that the incident light is either reflected at the desired locations in the molded body, or, for example, beam splitting or polarization separation is achieved.

The monolithic shaped body can be produced in any desired geometry, wherein the interfaces must have a sufficient optical surface quality. Technically, this is possible for example by the high-precision LIGA process and subsequent replication of molded parts made of polymer or low-melting glasses. The shaped body further comprises at least one interface permitting transmission of the incident light, an entry point, at least one splitter which effects beam splitting and thus splits the incident light and comprises at least one interference point at which the beam portions are recombined. Between the points of beam splitting and the interference point, at least one or more interfaces for beam deflection in the monolithic shaped body is required, which guide both partial beams by means of total reflection in an appropriate manner to the interference point.

The monolithic molded body according to the invention is in its geometric configuration the desired application customizable. In optical delay interferometers, the optical paths, which are also referred to as optical arms, are of different lengths after the beam splitting. By a suitable choice of the geometry and arrangement of the interfaces, the optical path of the light in an optical arm in the molded body can be extended by diverting this partial beam several times in the molding. The partial beam may alternatively be transported out of the molded body and be deflected back into this by a deflection mirror.

A significant advantage of the interferometer according to the invention is that a high degree of integration is achieved by the arrangement of the monolithic molded body, can be dispensed with optical coatings, as well as the time-consuming installation and adjustment of optical components.

Hereinafter, the invention with reference to an example and the 1 explained in more detail. The 1 shows the beam path in an interferometer, wherein the monolithic shaped body is designed such that the interferometer is designed as a delay interferometer.

About an entry point 1 light falls in the monolithic shaped body 2 of the interferometer and is via a geometric beam splitter 3 in two partial beams 4 . 5 divided up. A first part 5 of the incident light is at a first interface 6 with a first critical angle reflected by total reflection and an interference point 7 directed. A second part 4 of the incident light is at a second interface 3 reflected at a second critical angle and from the monolithic shaped body 2 out into a deflecting mirror 8th directed. The deflection mirror 8th is in the in 1 shown execution form symmetrical and includes two interfaces whose critical angle are the same. The part of the light 4 in the deflecting mirror 8th is deflected at the two interfaces in succession and is the deflection mirror 8th back into the monolithic moldings 2 in and there on the interference point 7 directed. The optical path of the second partial beam 4 is longer than the first partial beam 5 , so that at the interference point 7 an interference pattern corresponding to the different optical paths is created.

The beam splitter can be embodied here as a geometric or physical beam splitter. In a geometric beam splitter, the incident beam is spatially divided into two sub-beams by utilizing the spatial coherence of the injected light. Physical beam split the light in its intensity.

The monolithic molded article may also be used for polarization separation in the interferometer in the example shown by using an interface located at Brewster's angle to the incident light.

Furthermore, the monolithic molded body can be embedded in further functional structures, or be surrounded by them. These structures may also be monolithically bonded to the molding, e.g. B. by a common substrate. In addition to the function of targeted light guidance, these can serve as a defined stop and mounting structures.

LIST OF REFERENCE NUMBERS

1

entry point

2

monolithic shaped body

3

optical interface formed as a geometric beam splitter

4

second partial beam

5

first partial beam

6

Interface formed as a reflection point

7

interference point

8th

deflecting

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102005021783 A1 [0004]

Cited non-patent literature

• C. Solf, Development of Miniaturized Fourier Transform Spectrometers and Their Production with the LIGA Method, Dissertation, Universität Karlsruhe, (2004) [0004]
• O. Manzardo et. al. "Miniaturized lamellar grating interferometer based on silicon technology", Opt. Letters, Vol. 29 1437-1439, (2002) [0005]

Claims (7)

Microoptical interferometer comprising free-beam optical components, which are arranged in such a way that incident light is guided by free-space total optical reflection, characterized in that the free-beam optical components comprise one or more monolithic molded bodies ( 2 ) and wherein the monolithic shaped body ( 2 ) comprises optical interfaces and wherein the optical interfaces of the molding at least one entry point ( 1 ), at least one beam splitter ( 3 ), at least one reflection point ( 6 ), and at least one interference point ( 7 ). Microoptical interferometer according to claim 1, wherein the monolithic shaped body ( 2 ) consists of a transparent material for the wavelength of the incident light. Microoptical interferometer according to claim 1 or 2, wherein the monolithic shaped body ( 2 ) consists of a polymer material. Microoptical interferometer according to claim 1 or 2, wherein the monolithic shaped body ( 2 ) consists of glass. Microoptical interferometer according to one of claims 1 to 4, wherein the optical interfaces comprise optical critical angles for the division of the light. Microoptical interferometer according to one of claims 1 to 5, wherein the optical interfaces comprise optical critical angles for the polarization separation of the light. Microoptical interferometer according to one of claims 1 to 6, wherein the monolithic shaped body ( 2 ) has an asymmetric structure and the interferometer is designed as an optical delay interferometer.

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