Abstract:
The present disclosure relates to an optical device and technique for manipulating microscopic objects. The device includes a support to locate microscopic objects. A laser array assembly that includes a plurality of organic laser devices generates an image onto the support via an objective lens. A control device controls the plurality of the organic laser devices to vary the image on the support and manipulate the microscopic objects disposed on the support.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to organic lasers, and more specifically to a organic microcavity laser for manipulating microscopic objects.  
       BACKGROUND OF THE INVENTION  
       [0002]     Optical tweezers use light to manipulate microscopic objects as small as a single atom. The radiation pressure from a focused laser beam is able to trap and move small particles. In the biological area, these methods and instruments are used to apply forces in the pN-range and to measure displacements in the nanometer range of objects ranging in size from 10 nm to over 100 mm. In the most basic form a laser beam is focused by a high-quality microscope object to a spot on the specimen plan. The spot creates an “optical trap” which is able to hold a small particle at its center.  
         [0003]     The prior art as shown in  FIG. 1  illustrates an optoelectronic tweezers (OET) device  10  used to manipulate biological cells and micrometer-scale particles  15 . The cells or particles  15  which are to be manipulated are contained in a liquid (not shown) sandwiched between an upper transparent, conductive ITO-coated glass  20  and a lower photoconductive support structure  25  sitting on a glass substrate  27 . The photoconductive support structure  25  consists of several featureless layers of ITO-coated glass  30 , an n +  hydrogenated amorphous silicon (a-Si:H) layer  32 , an undoped a-Si:H layer  34 , and a silver nitride layer  36 . These two surfaces are biased with 10V pp  AC signal created by an AC signal generator  38 .  
         [0004]     A digital micro mirror display (DMD)  40  is illuminated by the light as indicated by arrow  45  from a light emitting diode (LED)  50 , creating an optical image  55  on the photoconductive support structure  25  via objective lens  57 . The projected light as indicated by arrows  60  turns on the virtual electrodes creating non-uniform electric fields enabling particle manipulation via dielectriophoresis (DEP) forces.  
         [0005]     Also known in the art are optical tweezers that rely entirely on optical forces to manipulate microscopic objects; they do not necessarily require dielectriophoresis (DEP) forces for the object manipulation. These devices have been extensively reviewed in the literature. For example, “Demonstration of trapping, motion control, sensing and fluorescence detection of polystyrene beads in a multi-fiber optical trap” by Cynthia Jensen-McMullin and Henry P. Lee, Optics Express, Vol. 13, No. 7, p. 2634 (4 Apr. 2005) describes an optical fiber-based embodiment of such an optical trapping system.  
         [0006]     Lasers have been known to be attractive alternative light sources to lamps for illuminator systems. Laser illumination offers the potential for simple, low-cost efficient optical systems, providing improved efficiency and higher contrast. One disadvantage of lasers for illuminator systems use has been the lack of a cost-effective laser source with sufficient power at appropriate visible wavelengths.  
         [0007]     Light valves that consist of a two-dimensional array of individually operable pixels arrayed in a rectangular geometry provide another component that enables pixilated laser illuminator systems. Examples of area light valves are reflective liquid crystal modulators such as the liquid-crystal-on-silicon (LCOS) modulators available from JVC, Three-Five, Aurora, and Philips, and micro-mirror arrays such as the Digital Light Processing (DLP) chips available from Texas Instruments. Advantages of two-dimensional modulators over one-dimensional array modulators and raster-scanned systems are the absence of scanning required, absence of streak artifacts due to nonuniformities in the modulator array, and immunity to laser noise at frequencies much greater than the frame refresh rate (≧120 Hz) in display systems. A further advantage of two-dimensional spatial light modulators is the tolerance for low spatial coherence of the illuminating beam. One-dimensional or linear light valves such as the Grating Light Valve (GLV) produced by Silicon Light Machines and conformal grating modulators require a spatially coherent illumination in the short dimension of the light valve.  
         [0008]     When using an area light valve in an illuminator system requiring the use of RGB laser arrays, though, it would be desired to use fully integrated two-dimensional laser arrays. One of the few laser technologies that are easily integrable in two dimensions is the vertical-cavity surface-emitting laser (VCSEL).  
         [0009]     VCSELs based on inorganic semiconductors (e.g. AlGaAs) have been developed since the mid-80&#39;s (S. Kinoshita et al., IEEE Journal of Quantum Electronics, Vol. QE-23, Number 6, [1987]). They have reached the point where AlGaAs-based VCSELs emitting at 850 nm are manufactured by a number of companies and have lifetimes beyond 100 years (K. D. Choquette et al., Proc. IEEE Vol. 85, No. 11, [1997]). With the success of these near-infrared lasers, attention in recent years has turned to other inorganic material systems to produce VCSELs emitting in the visible wavelength range (C. Wilmsen et al.,  Vertical - Cavity Surface - Emitting Lasers,  Cambridge University Press, Cambridge, 2001). There are many potential applications for visible lasers, such as, display, optical storage reading/writing, laser printing, and short-haul telecommunications employing plastic optical fibers (T. Ishigure et al., Electronics Letters Vol. 31, No. 6 [1995]). In spite of the worldwide efforts of many industrial and academic laboratories, much work remains to be done to create viable laser diodes (either edge emitters or VCSELs) that produce light output that spans the visible spectrum.  
         [0010]     In an effort to produce visible wavelength VCSELs it would be advantageous to abandon inorganic-based systems and focus on organic-based laser systems, since organic-based gain materials can enjoy a number of advantages over inorganic-based gain materials in the visible spectrum. For example, typical organic-based gain materials have the properties of low unpumped scattering/absorption losses and high quantum efficiencies. In comparison to inorganic laser systems, organic lasers are relatively inexpensive to manufacture, can be made to emit over the entire visible range, can be scaled to arbitrary size and, most importantly, are able to emit multiple wavelengths (such as red, green, and blue) from a single chip. Over the past number of years, there has been increasing interest in making organic-based solid-state lasers. The laser gain material has been either polymeric or small molecule and a number of different resonant cavity structures were employed, such as VCSEL (Kozlov et al., U.S. Pat. No. 6,160,828), waveguide, ring micro lasers, and distributed feedback (see also, for instance, G. Kranzelbinder et al., Rep. Prog. Phys. 63, pages 729-762 (2000) and M. Diaz-Garcia et al., U.S. Pat. No. 5,881,083). A problem with all of these structures is that in order to achieve lasing it was necessary to excite the cavities by optical pumping using another laser source. It is much preferred to electrically pump the laser cavities since this generally results in more compact and easier to modulate structures.  
         [0011]     A main barrier to achieving electrically pumped organic lasers is the small carrier mobility of organic material, which is typically on the order of 10 −5  cm 2 /(V-s). This low carrier mobility results in a number of problems. Devices with low carrier mobilities are typically restricted to using thin layers in order to avoid large voltage drops and ohmic heating. These thin layers result in the lasing mode penetrating into the lossy cathode and anode, which causes a large increase in the lasing threshold (V. G. Kozlov et al., J. Appl. Phys. Vol. 84, Number 8, pages 4096-4108 (1998)). Since electron-hole recombination in organic materials is governed by Langevin recombination (whose rate scales as the carrier mobility), low carrier mobilities result in orders of magnitude more charge carriers than singlet excitons; one of the consequences of this is that charge-induced (polaron) absorption can become a significant loss mechanism (N. Tessler et al., Appl. Phys. Lett. Vol. 74, Number 19, pages 2764-2766 (1999)). Assuming laser devices have a 5% internal quantum efficiency, using the lowest reported lasing threshold to date of ˜100 W/cm 2  (M. Berggren et al., Letters to Nature Vol. 389, page 466-469 (1997)), and ignoring the above mentioned loss mechanisms, would put a lower limit on the electrically-pumped lasing threshold of 1000 A/cm 2 . Including these loss mechanisms would place the lasing threshold well above 1000 A/cm 2 , which to date is the highest reported current density, which can be supported by organic devices (N. Tessler, et al., Advanced Materials (1998)), 10, No. 1, pages 64-68.  
         [0012]     One way to avoid these difficulties is to use crystalline organic material instead of amorphous organic material as the lasing media. This approach was recently taken (J. H. Schon, Science 289, 599 (2000)) where a Fabry-Perot resonator was constructed using single crystal tetracene as the gain material. By using crystalline tetracene larger current densities can be obtained, thicker layers can be employed (since the carrier mobilities are on the order of 2 cm 2 /(V-s)), and polaron absorption is much lower. This resulted in room temperature laser threshold current densities of approximately 1500 A/cm 2 .  
         [0013]     One of the advantages of organic-based lasers is that since the gain material is typically amorphous, devices can be formed inexpensively when compared to lasers with gain materials that require a high degree of crystallinity (either inorganic or organic materials). Additionally, lasers based upon organic amorphous gain materials can be fabricated over large areas without regard to producing large regions of single crystalline material. As a result they can be scaled to arbitrary size resulting in greater output powers. Because of their amorphous nature, organic-based lasers can be grown on a wide variety of substrates; thus, materials such as glass, flexible plastics, and Si are possible supports for these devices. Thus there can be significant cost advantages as well as a greater choice in usable support materials for amorphous organic-based lasers; the usage of single crystal organic lasers would obviate all of these advantages.  
         [0014]     An alternative to electrical pumping for organic lasers is optical pumping by incoherent light sources, such as, light emitting diodes (LEDs), either inorganic (M. D. McGehee et al. Appl. Phys. Lett. Vol. 72, No. 13, pages 1536-1538 [1998]) or organic (Berggren et al., U.S. Pat. No. 5,881,089). This possibility is the result of unpumped organic laser systems having greatly reduced combined scattering and absorption losses (˜0.5 cm −1 ) at the lasing wavelength, especially when one employs a host-dopant combination as the active media. Even taking advantage of these small losses, the smallest reported optically pumped threshold for organic lasers to date is 100 W/cm 2  based on a waveguide laser design (M. Berggren et al., Nature 389, 466 (1997)). Since off-the-shelf inorganic LEDs can only provide up to ˜20 W/cm 2  of power density, it is necessary to take a different route to make avail of optically pumping by incoherent sources. In order to lower the lasing threshold additionally, it is necessary to choose a laser structure which minimizes the gain volume; a VCSEL-based microcavity laser satisfies this criterion. Using VCSEL-based organic laser cavities should enable optically pumped power density thresholds below 5 W/cm 2 . As a result, practical organic laser devices can be driven by optically pumping them with a variety of readily available, incoherent light sources, such as LEDs. Furthermore, because the pump LEDs can be arrayed over an area, the organic laser can be built into two-dimensional arrays.  
       SUMMARY OF THE INVENTION  
       [0015]     In general terms, the present invention is an array of organic vertical cavity laser device for manipulating microscopic objects.  
         [0016]     One aspect of the present invention is a method of manipulating objects. The method includes providing a support for locating objects, providing a laser array assembly having a plurality of organic vertical cavity laser devices, imaging the plurality of organic laser devices onto the support, and manipulating the objects disposed on the support by controlling the plurality of the organic vertical cavity laser devices to vary an optical image on the support.  
         [0017]     Another aspect of the present invention is directed to a system for manipulating objects. The system includes a support to locate objects, a laser array assembly having a plurality of organic vertical cavity laser devices, an objective lens to project an image generated by the plurality of the organic vertical cavity laser devices onto the support, and a control device to control the plurality of the organic vertical cavity laser devices to vary the image on the support and manipulate the objects disposed on the support.  
         [0018]     Another aspect of the present invention is a method of manipulating objects. The method includes providing a support for locating objects, providing a combination illuminator having a plurality of illuminating components, and manipulating the objects disposed on the support by controlling the plurality of the organic vertical cavity laser devices to vary an optical image on the support.  
         [0019]     Yet another aspect of the present invention is a system of manipulating objects. The system includes a support to locate objects, a combination illuminator having a plurality of illuminating components, and an objective lens to project an image generated by the plurality of the organic vertical cavity laser devices onto the support, and a control device to control the plurality of the organic vertical cavity laser devices to vary the image on the support and manipulate the objects disposed on the support. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]      FIG. 1  is a schematic illustrating an optoelectronic tweezers (OET) device used to manipulate biological cells and micrometer-scale particles as disclosed in the prior art;  
         [0021]      FIG. 2A  is a schematic illustrating an optoelectronic tweezers (OET) device made in accordance with the present invention;  
         [0022]      FIG. 2B  is a schematic illustrating another embodiment of the optoelectronic tweezers (OET) device made in accordance with the present invention;  
         [0023]      FIG. 3  is a cross-section side view schematic of an optically pumped organic vertical cavity laser device;  
         [0024]      FIG. 4  is a cross-section side view schematic of an optically pumped organic vertical cavity laser with a periodically structured organic gain region;  
         [0025]      FIG. 5  shows an organic vertical cavity laser structure made in accordance with the present invention in which a two-dimensional arrangement of organic vertical cavity laser devices is depicted;  
         [0026]      FIG. 6A  depicts an organic vertical cavity laser structure in which sub-arrays of different wavelength organic vertical cavity laser devices are fabricated;  
         [0027]      FIG. 6B  depicts an organic vertical cavity laser structure in which sub-arrays may be dynamically tuned to different wavelengths;  
         [0028]      FIG. 6C  is a cross-section side view of an optically pumped tunable organic vertical cavity laser;  
         [0029]      FIG. 7  illustrates a view of the organic vertical cavity laser assembly comprising the organic vertical cavity laser array and a pump beam light source made in accordance with the present invention;  
         [0030]      FIG. 8  illustrates an optical intensity or illumination pattern created by the organic vertical cavity laser array of  FIGS. 6A and 6B  made in accordance with the present invention;  
         [0031]      FIG. 9A  illustrates another embodiment of the present invention where the optical illumination patterns from the digital micro mirror display and organic vertical cavity laser array assembly are combined to create a composite image in accordance with the present invention; and  
         [0032]      FIG. 9B  illustrates yet another embodiment of the present invention where the output from an inorganic vertical cavity laser and organic vertical cavity laser array assembly are combined to create a composite image in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0033]     Various embodiments of the present invention will be described in detail with reference to the drawings, wherein like reference numerals represent like parts and assemblies throughout the several views. Reference to various embodiments does not limit the scope of the invention, which is limited only by the scope of the claims attached hereto. Additionally, any examples set forth in this specification are not intended to be limiting and merely set forth some of the many possible embodiments for the claimed invention.  
         [0034]     Instead of using the digital micro mirror display (DMD)  40  and the light emitting diode (LED)  50  in  FIG. 1  and it&#39;s complicated assembly, it is advantageous to replace these two components with an array of organic lasers. Organic materials-based lasers can be fabricated over large areas and grown on a variety of substrates such as glass, silica and most importantly flexible plastics. Organic lasers are available in abroad range of output wavelengths allowing optimization with specific photoconductive material. In the present invention, the terminology describing organic vertical cavity laser devices (VCSELs) may be used interchangeably in a short hand fashion as “organic laser cavity devices.” Organic laser cavity structures are fabricated as large area structures and optically pumped with light emitting diodes (LEDs).  
         [0035]     In the embodiment shown in  FIG. 2A  the LED and micro mirror illumination source of the optoelectronic tweezers described in  FIG. 1  are replaced with an organic vertical cavity laser array assembly  70  which includes a pump light source as described in  FIGS. 3, 4 ,  5  and  7  and in U.S. Pat. No. 6,853,660, Spoonhower et al., incorporated herein by reference. The result is an inexpensive, high brightness, compact, and versatile illumination source whose light output can be tuned over a large wavelength range. The organic vertical cavity laser array assembly  70  consists of a plurality of organic vertical cavity lasers and is capable of easily producing any type of illumination pattern because of the individual addressability of and control of each laser in the array. Referring to  FIG. 2A , a schematic of an optoelectronic tweezers (OET) device  80  made in accordance with the present invention is illustrated. The LED  50  and micro mirror  40  illumination source described in  FIG. 1  are replaced with the organic laser array assembly  70 , which emits a laser beam  130  to form the optical image  85 . The image  85  may vary in time. For example, a time-varying projection of a series of concentric circles as shown in  FIG. 2A  where the radius of each concentric circles is reduced would cause the micrometer-scale particles  15  to move to the center of the circular pattern and become more concentrated in that spatial region. The organic laser array assembly  70  may be programmed to create a varying pattern of illumination suitable for this use. A computer controller  75  is used to establish the pattern of illuminated pixels in the organic laser array assembly  70 .  
         [0036]     The optical transmission of photoconductive support structure  25  varies with the optical wavelength. This so-called optical transmission spectrum can be quite complex, with several wavelengths where maximum transmission occurs. Referring to  FIG. 1 , the photoconductive support structure  25  consists of several featureless layers of ITO-coated glass  30 , an n +  hydrogenated amorphous silicon (a-Si:H) layer  32 , an undoped a-Si:H layer  34 , and a silver nitride layer  36 . The optical transmission of the photoconductive support structure  25  is determined by the optical transmission spectrum of each of the individual layers making up the photoconductive support structure  25 . One can optimize the performance of the optoelectronic (OET) tweezers device by selecting output wavelengths of the organic laser array assembly with pumped beam light source  70  corresponding to the maxima in the optical transmission spectrum of the photoconductive support structure  25 . Methods of selecting the output wavelength are disclosed in greater detail below.  
         [0037]     In another embodiment as shown in  FIG. 2B , the photoconductive support structure  25  is replaced by a support  37  that is movable in at least the x and y direction by a translator  90 , as shown by the optoelectronic tweezers (OET) device  81 . However, the embodiment is not limited to the x and y directions, and the support structure  25  can be moved in any suitable direction. This enables a larger control range for the position of the micrometer-scale particles  15 . Through the use of the translator  90  spatial regions of an extended support  37  are selected and the particles within that region are manipulated by varying the optical image  85  on the support  37 . The use of such a translator  90  to extend the range of light-based control is obvious to those skilled in the art. The embodiment shown in  FIG. 2B  also differs from the embodiment shown in  FIG. 2A  by the lack of elements necessary to establish an electric field and manipulate the micrometer-scale particles  15  by dielectriophoresis (DEP) forces. These elements include the photoconductive support structure  25 , the conductive ITO-coated glass  20 , and the AC signal generator  38 . In this embodiment, the forces used to manipulate and control the position of the micrometer-scale particles  15  arise from the intensity distribution of the optical image  85  itself. For example, a suitably bright spot with a Gaussian intensity profile will trap a particle  15 ; subsequent movement of the spot will control the position of the particle. In this case, the optimum wavelength is affected by the optical properties of the particles themselves. Particles with differing optical properties will experience differences in the manipulating forces with different light wavelengths. This physical phenomenon offers a mechanism for enhanced capability in the control of the particles position.  
         [0038]     A schematic of an organic vertical cavity laser device  100  is shown in  FIG. 3 . The substrate  105  can either be light transmissive or opaque, depending on the intended direction of optical pumping or laser emission. Light transmissive substrates  105  may be transparent glass, sapphire, or other transparent flexible materials such as plastic. Alternatively, opaque substrates including, but not limited to, semiconductor material (e.g. silicon) or ceramic material may be used in the case where both optical pumping and emission occur through the same surface. On the substrate is deposited a bottom dielectric stack  110  followed by an organic active region  115 . A top dielectric stack  120  is then deposited on the organic active region  115 . A pump beam  125  optically pumps the organic vertical cavity laser device  100 . The source of the pump beam  125  may be incoherent, such as emission from a light-emitting diode (LED).  
         [0039]     The preferred material for the organic active region  115  is a small-molecular weight organic host-dopant combination typically deposited by high-vacuum thermal evaporation. These host-dopant combinations are advantageous since they result in very small unpumped scattering/absorption losses for the gain media. It is preferred that the organic molecules be of small molecular weight since vacuum deposited materials can be deposited more uniformly than spin-coated polymeric materials. Host materials used in the present embodiment are selected such that they have sufficient absorption of the pump beam  125  and are able to transfer a large percentage of their excitation energy to a dopant material via Förster energy transfer. Those skilled in the art are familiar with the concept of Förster energy transfer, which involves a radiationless transfer of energy between the host and dopant molecules. An example of a useful host-dopant combination for red-emitting lasers is aluminum tris(8-hydroxyquinoline) (Alq) as the host and [4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran] (DCJTB) as the dopant (at a volume fraction of 1%). Other host-dopant combinations can be used for other wavelength emissions. For example, in the green a useful combination is Alq as the host and [10-(2-benzothiazolyl)-2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H,11H-[1]Benzopyrano[6,7,8-ij]quinolizin-11-one] (C545T) as the dopant (at a volume fraction of 0.5%). Other organic gain region materials can be polymeric substances, e.g., polyphenylenevinylene derivatives, dialkoxy-polyphenylenevinylenes, poly-para-phenylene derivatives, and polyfluorene derivatives, as taught by Wolk et al. in commonly assigned U.S. Pat. No. 6,194,119 B1, issued Feb. 27, 2001, and referenced herein. It is the purpose of the organic active region  115  to receive transmitted pump beam light  125  and emit laser light.  
         [0040]     The bottom and top dielectric stacks  110  and  120 , respectively, are preferably deposited by conventional electron-beam deposition and can comprise alternating high index and low index dielectric materials, such as, TiO 2  and SiO 2 , respectively. Other materials, such as Ta 2 O 5  for the high index layers, could be used. The bottom dielectric stack  110  is deposited at a temperature of approximately 240° C. During the top dielectric stack  120  deposition process, the temperature is maintained at around 70° C. to avoid melting the organic active materials. In an alternative embodiment, the top dielectric stack is replaced by the deposition of a reflective metal mirror layer. Typical metals used in the mirror layer are silver or aluminum, which have reflectivities in excess of 90%. In this alternative embodiment, both the pump beam  125  and the laser emission  130  would proceed through the substrate  105 . Both the bottom dielectric stack  110  and the top dielectric stack  120  are reflective to laser light over a predetermined range of wavelengths, in accordance with the desired emission wavelength of the laser cavity  100 .  
         [0041]     The use of a vertical microcavity laser with very high finesse allows a lasing transition at a very low threshold (below 0.1 W/cm 2  power density). This low threshold enables incoherent optical sources to be used for the pumping instead of the focused output of laser diodes, which is conventionally used in other laser systems. An example of a pump source is a UV LED, or an array of UV LEDs, e.g. from Cree (specifically, the XBRIGHT® 900 UltraViolet Power Chip® LEDs). These sources emit light centered near 405 nm wavelength and are known to produce power densities on the order of 20 W/cm 2  in chip form. Thus, even taking into account limitations in utilization efficiency due to device packaging and the extended angular emission profile of the LEDs, the LED brightness is sufficient to pump the laser cavity at a level many times above the lasing threshold.  
         [0042]     Organic lasers open up a more viable route to output that spans the visible spectrum. Organic based gain materials have the properties of low un-pumped scattering/absorption losses and high quantum efficiencies. VCSEL based organic laser cavities can be optically pumped using an incoherent light source such as light emitting diodes (LED) with lasing power thresholds below 5 W/cm 2 .  
         [0043]     One advantage of organic-based lasers is that since the gain material is typically amorphous, devices can be formed inexpensively when compared to lasers with gain materials that require a high degree of crystallinity. Lasers based on amorphous gain materials can be fabricated over large areas without regard to producing large regions of a single crystalline material and can be scaled to arbitrary size resulting in greater power output. Because of the amorphous nature, organic based lasers can be grown on a variety of substrates, thus, materials such as glass, flexible plastics and Si are possible supports for these devices.  
         [0044]      FIG. 4  is a cross-section side view schematic of an optically pumped organic vertical cavity laser with a periodically structured organic gain region. The efficiency of the laser is improved further using an active region design as depicted in  FIG. 4  for the organic vertical cavity laser device  100 . The organic active region  115  includes one or more periodic gain regions  135  and organic spacer layers  140  disposed on either side of the periodic gain regions  135 . The spacer layers  140  are arranged so that the periodic gain regions  135  are aligned with antinodes  145  of the device&#39;s standing wave electromagnetic field. This is illustrated in  FIG. 4  where the laser&#39;s standing electromagnetic field pattern  150  in the organic active region  115  is schematically drawn. Since stimulated emission is highest at the antinodes  145  and negligible at nodes  155  of the electromagnetic field, it is inherently advantageous to form the active region  115 . The organic spacer layers  140  do not undergo stimulated or spontaneous emission and largely do not absorb either the laser emission  130  or the pump beam  125  wavelengths. An example of a spacer layer  140  is the organic material 1,1-Bis-(4-bis(4-methyl-phenyl)-amino-phenyl)-cyclohexane (TAPC). TAPC works well as the spacer layer material since it largely does not absorb either the laser emission  130  or the pump beam  125  energy and, in addition, its refractive index is slightly lower than that of most organic host materials. This refractive index difference is useful since it helps in maximizing the overlap between the electromagnetic field antinodes and the periodic gain region(s)  135 . As will be discussed below, employing periodic gain region(s)  135  instead of a bulk gain region results in higher power conversion efficiencies and a significant reduction of the unwanted spontaneous emission.  
         [0045]     The placement of the periodic gain region(s)  135  is determined by using the standard matrix method of optics (Corzine et al. IEEE Journal of Quantum Electronics, Volume 25, No. 6, June 1989). To get good results, the thicknesses of the periodic gain region(s)  135  need to be at or below 50 nm in order to avoid unwanted spontaneous emission.  
         [0046]      FIG. 5  illustrates one embodiment of an organic laser cavity structure in which a two-dimensional arrangement of a plurality of organic vertical cavity laser devices is depicted. Fabricating organic laser cavity devices  200  in a regular pattern that extends in 2 dimensions forms such a two-dimensional organic laser cavity structure  205 . The inter-pixel regions  210  generally consist of non-lasing portions of the structure that separate the organic laser cavity devices  200 .  
         [0047]      FIG. 6A  depicts an embodiment of an organic laser cavity structure  227  in which sub-structures of different wavelength organic laser cavity devices  200  are fabricated. A multiwavelength organic laser cavity structure  227  has sub-structures of red (r)  226   a,  green (g)  226   b,  and blue (b)  226   c  regions, separated by interpixel regions  210 . The two-dimensional organic laser cavity structure  227  produces a multiwavelength light output, where the laser light emission is designed to occur at discrete wavelengths in the red (R), green (G), and blue (B) regions of the optical spectrum. The red region of the optical spectrum approximately corresponds to the wavelength range of 600-650 nm. The green region of the optical spectrum approximately corresponds to the wavelength range of 500-550 nm, and the blue region of the optical spectrum approximately corresponds to the wavelength range of 450-500 nm. With the proper design of the organic laser cavity device  200 , the light output wavelength can be specified throughout the visible optical spectrum (approximately 450-700 nm). It is to be understood that different wavelength pump-beam light can be used to produce a substantially single wavelength output. This can be accomplished through the proper design of the dielectric stack materials and thicknesses, the choice of the organic active region  115  materials ( FIG. 4 ), and the cavity dimensions. Alternatively, single wavelength pump-beam light can produce multiple substantially different wavelength outputs. Again this is accomplished by design of the various organic laser cavity devices  200  in the structure. It is also to be understood that any of the organic laser cavity structures can be designed and fabricated so as to produce a multiwavelength light output suitable for the application at hand. In addition the degree of coherence of the various organic laser cavity devices  200  may be controlled via a number of mechanisms. One such mechanism involves lowering the microcavity finesse to reduce the laser coherence.  
         [0048]     Changes in both the bottom dielectric stack  110  and the top dielectric stack  120  ( FIG. 4 ) can reduce the reflectivity at the lasing wavelength and would affect the laser coherence. Alternatively, individual organic laser cavity devices  200  may have their light output combined optically with reduced coherence if the distance in the array  70  ( FIG. 2A ) is large enough to preclude coupling of the individual organic laser cavity devices  200 . Separation distances larger that approximately 20 micron would decouple the individual organic laser cavity devices  200 .  
         [0049]      FIG. 6B  depicts an organic laser cavity structure  227  in which sub-arrays  285  comprised of optically pumped organic vertical cavity laser systems  300  may be dynamically tuned to different wavelengths.  
         [0050]      FIG. 6C  is a cross-section side view of an optically pumped organic vertical cavity laser system  300 . The system  300  employs a multi-layered film structure  305  with a periodically structured organic gain region and with MEMs (micro-electromechanical system) device for changing the optical path length of the laser cavity. The vertical cavity laser system  300  is best described by considering two separate subsystems: the multi-layered film structure  305  and the micro-electromechanical mirror assembly  310 . The multi-layered film structure  305  consists of the substrate  105 , the bottom dielectric stack  110 , the organic active region  115 , and one or more index matching layers  290  and  295 . In this case, the substrate  105  is transmissive for light of the pump beam  125 . Pump beam  125  light is received by the multi-layered film structure  305  and produces spontaneous emission. The top dielectric stack  345  and the bottom dielectric stack  110  constitute the end mirrors of the organic laser cavity. The micro-electromechanical mirror assembly  310  consists of a bottom electrode  315 , a support structure  320 , a top electrode  325 , support arms  330 , an air gap  335 , a mirror tether  340 , and the top dielectric stack  345 . Laser emission  130  occurs from the top dielectric stack  345 . A voltage source (not shown) applied between the bottom electrode  315  and the top electrode  325  changes the thickness t, of the air gap  335  via electrostatic interaction and thereby varies the cavity length of the organic laser cavity device. This variation of the organic laser cavity length causes a wavelength variation of the optically pumped tunable vertical cavity organic laser system  300 . A tunable organic vertical cavity laser system is described in U.S. Pat. No. 6,970,488 by J. P. Spoonhower et. al. and is hereby incorporated by reference.  
         [0051]      FIG. 7  illustrates a view of the organic vertical cavity laser assembly  70  comprising the vertical cavity organic laser array  227  and a pump beam light source  250  for optically pumping light  255  to the organic laser array  227 . In the embodiment shown the pump beam light source  250  is an array formed by individual light sources  253  whose pattern matches the pattern of the vertical cavity organic laser array  227 . Individual light emitting diodes (LEDs) are examples of the individual light sources  253 . The illuminating pattern  207  once imaged is used to manipulate the particles  15  ( FIG. 1 ) position.  
         [0052]      FIG. 8  illustrates one embodiment of a multiwavelength organic laser cavity array  227 . The array  227  uses sub-structures of red (r)  226   a,  green (g)  226   b,  and blue (b)  226   c  to create an illuminated pattern  207  that is focused onto the photoconductive support structure  25  via lens  57  as shown in  FIG. 2A  or on a support  37  as shown in  FIG. 2B . The projected optical image  85  ( FIG. 2A ) is used to manipulate the particles on the support  25 , for example, via either dielectriophoresis or photon forces as previously discussed. It has been found the different particles react differently to particular wavelengths the multiwavelength organic laser cavity array  227  can be wavelength tuned to produce the image  85  with the optimum response to manipulate a particular particle  15 , for example, within a mixture of particles.  
         [0053]      FIG. 9A  is another embodiment illustrating an optical manipulator illuminated by patterned organic microcavity lasers. Light from the digital micro mirror display (DMD)  40  illuminated by the light emitting diode (LED)  50  is combined with the optical illuminant  207  from organic vertical cavity laser array assembly  70  by a beam splitter  260  as indicated by arrows  270  and  275  creating a composite optical image  265  which is focused onto the support  37  via objective lens  57 .  
         [0054]      FIG. 9B  is yet another embodiment illustrating an optical manipulator illuminated by patterned organic microcavity lasers. In  FIG. 9B , the light output from an inorganic laser  280  providing a spatially uniform illuminant is combined with the optical illuminant  207  from organic vertical cavity laser array assembly  70  by a beam splitter  260  as indicated by arrows  270  and  275  creating a composite optical image  265  which is focused onto the support  37  via objective lens  57 . In both  FIGS. 9A and 9B  the use of the additional illuminating light from the inorganic laser  280 , or the light from the LED  50  modified by the digital micro mirror display (DMD)  40  to create an illuminating pattern offsets the available form the organic vertical cavity laser array assembly  70  when used alone. This combination of illuminants can provide greater flexibility in manipulating the positions of particles  15 .  
         [0055]     The various embodiments described above are provided by way of illustration only and should not be construed to limit the invention. Those skilled in the art will readily recognize various modifications and changes that may be made to the present invention without following the example embodiments and applications illustrated and described herein, and without departing from the true spirit and scope of the present invention, which is set forth in the following claims.  
       PARTS LIST  
       [0000]    
       
           10  optoelectronic (OET) tweezers device  
           15  micrometer-scale particles  
           20  conductive ITO-coated glass  
           25  photoconductive support structure  
           27  glass substrate  
           30  ITO-coated glass  
           32  n +  hydrogenated amorphous silicon (a-Si:H) layer  
           34  undoped a-Si:H layer  
           36  silver nitride layer  
           37  support  
           38  AC signal generator  
           40  digital micro mirror display (DMD)  
           45  arrow  
           50  light emitting diode (LED)  
           55  image  
           57  objective lens  
           60  arrow  
           70  organic vertical cavity laser array assembly with pumped beam light source  
           75  computer controller  
           80  optoelectronic (OET) tweezers device  
           85  image  
           90  translator  
           100  organic vertical cavity laser device  
           105  substrate  
           110  bottom dielectric stack  
           115  organic active region  
           120  top dielectric stack  
           125  pump beam  
           130  laser beam/emission  
           135  periodic gain regions  
           140  organic spacer layers  
           145  antinodes  
           150  electromagnetic field pattern  
           155  nodes  
           200  organic laser cavity device  
           205  two-dimensional organic laser cavity structure  
           207  pattern  
           210  inter-pixel regions  
           226   a, b, c,  red, green, blue  
           227  multiwavelength organic laser cavity structure  
           230  illuminated pattern  
           250  pumped beam light source  
           253  light sources  
           255  pumped light  
           260  beam splitter  
           265  composite image  
           270  arrow  
           275  arrow  
           280  inorganic laser.  
           285  sub-arrays  
           290  index matching layers  
           295  index matching layers  
           300  optically pumped organic vertical cavity laser system  
           305  multi-layered film structure  
           310  micro-electromechanical mirror assembly  
           315  bottom electrode  
           320  support structure  
           325  top electrode  
           330  support arms  
           335  air gap  
           340  mirror tether  
           345  top dielectric stack