Organic vertical-cavity surface-emitting lasers ("OVCSELs"), in which a thin layer of organic material is disposed between highly reflective mirrors to thereby form a vertical cavity within a stacked arrangement. The lasers of the present invention each comprise a first mirror layer; a layer of active organic material over the first mirror layer; and a second mirror layer over the layer of first active organic material. The active organic material lases when pumped to thereby produce laser light. The present invention provides for optical semiconductor lasers with desired properties such as narrow bandwidth emission, the minimal use of active organic materials, and the facilitation of wavelength tuning and electrical pumping.

FIELD OF THE INVENTION 
The present invention relates to the field of light emitting devices, in 
particular, to organic semiconductor lasers. 
BACKGROUND INFORMATION 
Several recent publications have reported phenomena such as 
superluminescence and amplified spontaneous emission in polymeric organic 
light emitters such as conjugated polymers. (N. Tessler et al., Nature 
382, 695 (1996); F. Hide et al., Science 273, 1833 (1996), both of which 
are incorporated herein by reference). The materials used in those 
emitters were spin-coated from a solution of the polymer or its chemical 
precursors. Optically pumped, stimulated emission from organic laser dyes, 
introduced into inert, spin-coated polymers or gels has been described in 
the literature. (R. E. Hermes, et al., Appl. Phys. Lett. 63, 877 (1993); 
M. N. Weiss et al., Appl. Phys. Lett. 69, 3653 (1996); H. Kogelnik et al., 
Appl. Phys. Lett. 18, 152 (1971); M. Canva et al., Appl. Opt., 34, 428 
(1995), each of which is incorporated herein by reference). 
When compared with other electrolumninescent materials, however, spun-on 
polymeric materials do not exhibit particularly good thickness uniformity, 
ability to achieve extremely high materials purity, operating lifetimes, 
and ease of integration with other conventional semiconductor fabrication 
processes. In the field of organic light emitting devices (OLEDs) for flat 
panel display applications, for example, small molecule OLEDs currently 
offer better operating lifetimes by an order of magnitude over their 
spin-coated, polymeric analogs. (L. J. Rothberg et al., "Status of and 
Prospects for Organic Electroluminescence", J. Mater. Res. 1996, 11:3174; 
N. C. Greenham et al., "Semiconductor Physics of Conjugated Polymers", 
Solid State Physics 1995, 49:1, both of which are incorporated herein by 
reference). 
There is much recent interest in lasing action and stimulated emission in 
thin films of small molecular weight organic semiconductors and polymers 
as organic semiconductor lasers ("OSLs"). The low cost of organic 
materials and ability to grow them as quasi- and non-epitaxial thin films 
facilitates integration of OSLs with other optoelectronic devices, making 
them attractive for a number of applications. The particular optical and 
electronic properties of organic semiconductors result in OSL performance 
that is significantly more temperature stable than conventional inorganic 
laser diodes, a potential advantage in optical communications and sensor 
applications. For example, the lasing action in optically-pumped slab 
waveguide structures of vacuum-deposited thin films of small molecular 
weight organic semiconductors has been recently demonstrated. (See V. G. 
Kozlov et al., Conf on Lasers and Electro-optics CLEO '97, CPD-18, Opt. 
Soc. Am., Baltimore, Md., May 1997, incorporated herein by reference). The 
output power, differential quantum efficiency, and emission wavelength of 
these organic semiconductor lasers (OSLs) were found to be significantly 
more stable to changes in temperature than conventional inorganic laser 
diodes. This benefit of organic laser structures combined with the 
inherent advantages of organic semiconductors such as low cost, quasi- and 
non-epitaxial growth (S. R. Forrest et al., Phys. Rev. B 49, 11309 (1994), 
incorporated herein by reference), and ease of integration with other 
optoelectronic devices, provides strong motivation for further research. 
Presently, there is an interest in the development of OSL structures that 
result in desired OSL properties svch as narrow bandwidth emission, the 
minimal use of active organic materials, and the facilitation of 
wavelength tuning and electrical pumping. 
SUMMARY OF THE INVENTION 
The present invention provides organic vertical-cavity surface, emitting 
lasers ("OVCSELs"), in which a thin layer of organic material is disposed 
between highly reflective mirrors to thereby form a vertical cavity within 
a stacked arrangement. More specifically, the lasers of the present 
invention each comprise a first mirror layer; a layer of active organic 
material over the first mirror layer; and a second mirror layer over the 
layer of first active organic material. The active organic material lases 
when pumped to thereby produce laser light-that passes through one or both 
of the first and second mirror layers. 
In one aspect, the present invention relates to optically-pumped OVCSELs. 
Embodiments of such OVCSELs include a source of optical pump energy for 
pumping the active organic material. 
In another aspect, the present invention relates to electrically-pumped 
OVCSELs. In embodiments of such OVCSELs, the active organic material is 
electroluminescent and is disposed between a pair of electrodes. The 
active organic material is pumped when an electric current is passed 
between the electrodes.

DETAILED DESCRIPTION 
The present invention is directed to organic vertical-cavity 
surface-emitting lasers (OVCSELs). The present invention represents the 
first known successful demonstration of lasing action in a small molecular 
weight organic semiconductor microcavity structure associated with a clear 
threshold in the output power, a well-defined laser beam, cavity modes, 
and spectral line narrowing of emission above threshold to less than 1 
.ANG.. The high gain in these films is sufficient to generate lasing even 
in cavities with active regions less than 500 nm thick, thereby minimizing 
the amount of active organic material required for operation. The device 
of the present invention represents a significant advance toward realizing 
a new class of semiconductor laser diodes based on organic thin films. 
The OVCSELs of the present invention are applicable to a wide variety of 
applications, including telecommunications, printing, optical 
downconversion, semiconductor circuit etching, thermal processing (e.g., 
marking, soldering and welding), spectroscopy, vehicular control and 
navigation, measurement devices, optical memory devices, displays, 
scanners, pointers, games and entertainment systems and sensors. 
FIG. 1 shows a cross section of a laser cavity structure 100 in accordance 
with an embodiment of the present invention. In this structure, an active 
organic material layer 110 is disposed between a first mirror layer 111 
and a second mirror layer 112 to thereby form a cavity of thickness, t. 
The organic material in layer 110 is "active" in that it lases when pumped 
by optical or electrical means to thereby produce laser light. The first 
and second mirror layers 111, 112 each reflect a substantial amount of the 
light produced by the layer 110 so that only coherent laser light passes 
through layers 111, 112, the laser light having a desired wavelength and 
characterized by a narrow bandwidth. The first and second mirror layers 
111, 112 each preferably reflect at least 90%, more preferably 95%, and 
most preferably 98%, of the light produced by the pumping of layer 110. If 
the first and second mirror layers 111, 112 reflect substantially the same 
percentage of light emitted from layer 110, the passage of light through 
both first and second mirror layers 111, 112 will be substantially equal, 
as shown in FIG. 1. If, for example, the second mirror layer 112 reflects 
a greater percentage of light than first mirror layer 111, however, then 
the passage of light will be primarily through the first mirror layer 111 
provided that the absorption characteristics of the first and second 
mirror layers are equal. 
FIG. 2 shows an optically-pumped OVCSEL structure 200, in accordance with 
an embodiment of the present invention. A first mirror layer 111, a layer 
of active organic material 110 and a second mirror layer 112 are disposed 
on a substantially transparent substrate 113. The layer of active organic 
material 110 is pumped by incident optical pump energy 115. The source of 
optical pump energy (not shown) is any suitable source of intense light, 
such as a nitrogen laser. 
The first and second mirror layers 111, 112, are any suitable reflective 
materials or structures. A preferred structure for the first mirror layer 
111 is a distributed Bragg reflector ("DBR") dielectric mirror stack. DBR 
mirrors are commercially available and consist of .lambda./4 thick 
dielectric layers, where .lambda. represents the wavelength of the DBR 
mirror reflective stopband. DBR mirrors thus render the ability to control 
the OVCSEL output spectrum, which in turn narrows the linewidth of such 
output. DBR mirrors are typically characterized by reflectivities in 
excess of 99%. The second mirror 112 is preferably a DBR mirror or a layer 
of reflective metal or alloy such as silver, platinum, aluminum, 
magnesium-aluminum alloy, or combinations thereof. Metal mirrors typically 
have reflectivities in excess of 90%, but absorb more light than do DBR 
mirrors. When the second mirror 112 comprises a metal, the OVCSEL 
structure 200 preferably includes an organic buffer layer 114 to reduce 
quenching of the organic material in the layer 110 at the organic/metal 
interface with the layer 112. In the embodiment shown in FIG. 2, the 
combined reflectivity and absorption of the second mirror layer 112 is 
greater than that of the first mirror layer 111, thus resulting in laser 
emission 116 through the first mirror layer 111. 
The substrate 113 is any suitable transparent substrate such as quartz, 
glass, sapphire or plastic. The substrate 113 is limited to those 
materials which are transparent to the wavelengths of incident optical 
pumping energy and of laser light produced by layer 110. 
In all embodiments of the present invention, the active organic material in 
layer 110 comprises host and dopant molecules. The pump energy imparted to 
layer 110 is absorbed by the host molecule and is non-radiatively 
transferred by a dipole-dipole transition to the dopant molecule. For this 
to occur, the emission spectrum of the host must overlap with the 
absorption spectrum of the dopant. The resulting efficient "Forster" 
energy transfer requires only a low concentration of dopant molecules, 
which in turn reduces the lasing threshold, increases laser efficiency, 
and extends operational lifetime. The host materials used in the present 
invention are selected from any materials that provide good charge 
transport and are able to transfer energy to a dopant material via Forster 
energy transfer or carrier capture. In addition, the rate of energy 
transfer to the dopant must be faster than the non-radiative recombination 
in the host. The dopant materials used in the present invention are any 
highly efficient luminescent molecules having luminescence (lasing) 
emission in the same spectral range as the transparency region of the 
host:dopant system. Exemplary host-dopant systems for use as the active 
organic material in the present invention, and some of their associated 
lasing characteristics are set forth in Table I. 
TABLE I 
______________________________________ 
Exemplary active organic materials for use in the 
OVCSELs of the present invention. 
Operating 
Lifetime 
Lasing Lasing (# of pump 
Wavelength Threshold 
laser 
Host Dopant (nm) (.mu.J/cm.sup.2) 
pulses) 
______________________________________ 
Alq.sub.3 
DCM 615-660 3 &gt;10.sup.6 
Alq.sub.3 
DCM2 655-700 2.5 &gt;10.sup.6 
Alq.sub.3 
Rhodamine 6G 
610-625 30 10.sup.3 
CBP Perylene 485 5 &gt;10.sup.5 
CBP Coumarin 47 460 15 10.sup.3 
CBP Coumarin 30 510 15 -- 
______________________________________ 
The formulae for the chemicals known as DCM (Exciton Inc. of Dayton, Ohio), 
Alq.sub.3, CBP, DCM2 (Exciton Inc. of Dayton, Ohio), Rhodamine 6G, 
Coumarin 47 and Perylene are shown in FIGS. 3A-3G, respectively. The 
organic materials used in the present invention are deposited by any 
suitable technique, such as by vacuum thermal evaporation. 
The present invention includes embodiments in which the laser emission is 
tunable to a specific wavelength. FIG. 4 shows an example of an 
optically-pumped, tunable OVCSEL 250 in accordance with an embodiment of 
the present invention. In this embodiment, the thickness, t, of the layer 
110 of active organic material changes monotonically from the left edge 
117 to the right edge 118 of the structure. By changing the thickness of 
the OVCSEL cavity, the emission wavelength is tunable by as much as 50 nm 
or more, due to the wide gain spectrum of the lasing material in layer 
110. Such thickness variation is achieved, for example, by masking the 
substrate with a sliding shadow mask during growth of layer 110. The 
tunable OVCSEL is pumped by a pump beam 115, which excites the active 
organic material of layer 110 at a point Xo, which is at a distance d away 
from the right edge 118. The wavelength of laser emission 116 is a 
function of the cavity thickness t and the index of the organic material 
in layer 110. By changing the position of point Xo, a different section of 
the OVCSEL structure 250 (having a different thickness, t) is excited by 
pump beam 115, thus resulting in a different wavelength of emission 116. 
Changing the position of Xo by varying d is accomplished by, for example, 
moving the OVCSEL structure 250, moving the position or angle of the pump 
beam 115, or both. As an example, the inventors have changed the laser 
emission of an optically-pumped Alq.sub.3 :DCM laser of the present 
invention from 598 to 635 nm by changing the thickness of layer 110 from 
430 to 500 nm. 
FIG. 5 shows an electrically-pumped OVCSEL structure 300, in accordance 
with an embodiment of the present invention. A first mirror layer 111, a 
layer of active organic material 110 and a second mirror layer 112 are 
disposed on a substantially transparent substrate 113. If the first and 
second mirror layers 111, 112 are not able to function as electrodes, or 
alternatively if it is preferable to have separate electrodes, a first 
electrode 120 is disposed between the first mirror layer 111 and the layer 
of active organic material 110, and a second electrode 121 is disposed 
between the layer of active organic material 110 and the second mirror 
layer 112. In this embodiment, the organic material in layer 110 is 
electroluminescent such that it is pumped to produce laser light when an 
electric current is passed therethrough. As is known in the art, the 
organic material in layer 110 typically consists of three sub-layers: a 
hole transporting layer ("HTL") 110a, an emissive layer ("EL") 110b, and 
an electron transporting layer ("ETL") 110c. First and second electrodes 
120, 121 (in the embodiment shown in FIG. 5, first and second electrodes 
are anode and cathode, respectively) are substantially transparent to the 
light emitted by layer 110b, and preferably comprise indium-tin-oxide or 
any other transparent conducting material. 
In one embodiment of the present invention, multiple electrically-pumped 
OVCSEL structures are placed in a stacked arrangement 350, as shown in 
FIG. 6, for the emission of laser light of various colors. The stacked 
arrangement 350 includes the structure 300 as shown in FIG. 5, but also 
includes a third mirror layer 211, a third electrode 220, sublayers 210a, 
210b, and 210c (corresponding to HTL, EL and ETL layers, respectively) of 
a second active organic material, a fourth electrode 221, and a fourth 
mirror layer 212 as shown in FIG. 6. As in the OVCSEL structure 300, the 
electrodes 120, 121, 220 and 221 are only necessary in the stacked 
arrangement 350 if the respective mirror structures 111, 112, 211 and 212 
cannot function as electrodes, or alternatively if it is preferable to 
have electrodes separate from the mirror structures. Although only two 
OVCSEL structures are shown in the stacked arrangement 350, the present 
invention includes embodiments in which three or more OVCSEL structures 
are stacked in a unitary structure. The stacking of OVCSEL structures 
facilitates the lasing of multiple colors, each from a respective OVCSEL, 
alone or in any combination. 
The present invention includes electrically-pumped OVCSELs that are tunable 
to specific wavelengths. FIG. 7 shows an example of such a tunable OVCSEL 
351 in accordance with an embodiment of the present invention. As 
described for the optically-pumped tunable OVCSEL 250, the laser emission 
wavelength of OVCSEL 351 is tunable by varying the thickness t of the 
OVCSEL cavity. The variation in t is accomplished by controlling the 
distance t1 between the second electrode 121 and the second mirror layer 
112. The distance t1 is varied by the controlled movement of the second 
mirror layer 112 towards or away from the second electrode 121, or 
vice-versa. Optical lens 130 is disposed between the second electrode 121 
and the second mirror layer 112 to permit the variation in t1 without 
losing control of the laser light emitted from layer 110b. 
All embodiments of the present invention optionally include guiding and 
cladding layers around the organic layers to help minimize waveguiding 
losses in the organic layers. For example, waveguide optical losses in 
organic layers of thickness 150 nm are often as high as 1000 cm.sup.-1 or 
more where metal electrodes are used in electroluminescent devices. A 
structure 400 as shown in FIG. 8 is used to minimize such losses. 
Structure 400 includes guiding layers 161 and 162 immediately adjacent to 
the organic layer(s) 110, and cladding layers 160 and 163 immediately 
adjacent to the guiding layers 161 and 162, respectively. As is known in 
the art and previously discussed, if layer 110 comprises an 
electroluminescent material, it may actually comprises multiple sublayers 
(i.e., HTL, EL and ETL layers). The guiding layers 161, 162 are highly 
transparent to minimize optical losses, and are characterized by a high 
refractive index. The cladding layers 160, 163 are also transparent but 
possess a lower refractive index than the guiding layers 161, 162. The 
cladding layers 160, 163 also generally have higher conductivities than 
the guiding layers 161, 162, as one of the primary purposes of cladding 
layers 160, 163 is to conduct electrical current. The structure 400 
reduces the confinement of emitted light in organic layer(s) 110, thus 
reducing optical losses to as low as 10 cm.sup.-1 or less. The structure 
400 is optionally used with any of the optically- or electrically-pumped 
embodiments of the present invention. For example, when used with the 
optically-pumped embodiment 200 of the present invention, the structure 
400 is substituted for the layer of active organic material 110 in FIG. 2. 
Likewise, when used with the electrically-pumped embodiment 300, the 
structure 400 is substituted for the sub-layers 110a, 110b and 110c such 
that the structure 400 is sandwiched by the electrodes 120 and 121. When 
used with the electrically-pumped embodiment, the guiding and cladding 
layers 160, 161, 162, 163 must be sufficiently conductive to provide 
charge carriers to the conductive layer(s) 110 from the electrodes 120, 
121. It is preferred, however, that the conductivity of guiding layers 
161, 162 is less than that of cladding layers 160, 163, which have a 
conductivity less than that of the surrounding electrodes 120, 121. The 
preferred material for the guiding and cladding layers 160, 161, 162, 163 
is indium-tin-oxide, the refractive index, conductivity and transparency 
of which is varied, for example, by varying oxygen content. 
The present invention is further described with reference to the following 
non-limiting example. 
EXAMPLE 
As one example of the embodiment shown in FIG. 2, an OVCSEL 200 was formed 
comprising an active layer 110 of tris-(8-hydroxyquinoline) aluminum 
("Alq.sub.3 ") doped with DCM laser dye. The thickness of the active layer 
110 was 500 nm. The concentration of DCM laser dye in the layer 110 was 3% 
by weight. The active layer 110 was deposited onto the first mirror layer 
111 (a DBR mirror in this example) by thermal evaporation at 
5.times.10.sup.-7 Torr. Buffer layer 114 comprised Alq.sub.3 and was 
deposited over the active layer 110, and a silver mirror layer 112 was 
deposited over the buffer layer 114. The thicknesses of the buffer layer 
114 and the DBR mirror layer 111 were 20 nm and 200 nm, respectively. The 
DBR mirror layer 111 had a &gt;99% reflective stopband between 600 nm and 700 
nm, while the reflectivity of the silver mirror was calculated to be 91%. 
The OVCSEL 200 was optically pumped using a nitrogen laser (.lambda.=337 
nm), which generated 500 ps pulses at a 50 Hz repetition rate. The pump 
beam was aimed incident through the DBR mirror 111 and was focused to a 
spot approximately 100 .mu.m across on the organic film surface. At the 
wavelength of the exciting laser (i.e., .lambda.=337 nm) the DBR mirror 
111 exhibited a transmittance of about 80%. In this example, the substrate 
113 comprised quartz, which is transparent to a pump beam characterized by 
.lambda.=337 nm. 
The emission spectrum in the substrate normal direction (with a 15.degree. 
full angle acceptance cone) was analyzed by a spectrograph using a 
charge-coupled device camera with a wavelength resolution of 1 .ANG.. To 
avoid material degradation, all measurements were performed in a dry 
nitrogen environment. 
FIG. 9 shows the spontaneous emission spectrum of the OVCSEL 200 just below 
the lasing threshold. A cavity mode was observed at .lambda.=635 nm. At 
.lambda.&lt;600 nm and .lambda.&gt;700 nm, the spontaneous emission is filtered 
by the modulation in the DBR transmission spectrum resulting in the broad 
satellite peaks observed. The spectrum above the lasing threshold, 
corresponding to an energy of E.sub.TH =300 .mu.J/cm.sup.2, is completely 
dominated by the high gain, spectrally narrow laser emission, as shown in 
FIG. 10. 
FIG. 11 shows the high resolution emission spectra from the OVCSEL 200 at 
increasing excitation levels near the lasing threshold. Pump energies and 
the spectral full width at half maximum are indicated. The transition from 
the 12 .ANG. wide spontaneous emission peak, spectrally filtered by the 
microcavity below threshold, to the resolution-limited, &lt;1 .ANG. full 
width spectral line due to laser emission above threshold, is clearly 
observed. The spectral width of the peak below threshold is related to the 
finesse (the ratio of microcavity mode spacing to a single mode linewidth) 
of the microcavity, with additional broadening due to the presence of 
several transverse modes. Mode competition above threshold confines lasing 
to only a few of the transverse modes, leading to a concomitant reduction 
in the emission linewidth. The left inset of FIG. 11 shows 
(0.4.+-.0.1).ANG. broad emission line of an OVCSEL with a cavity thickness 
of 475 nm. Accounting for the (0.2.+-.0.1).ANG. instrument resolution, the 
Gaussian full-width-at-half-maximum of the lasing line is calculated to be 
(0.2.+-.0.1).ANG.. 
FIG. 12 shows the dependence of the laser output power on input excitation, 
clearly indicating a threshold at a pump energy density of E.sub.TH =300 
.mu.J/cm.sup.2. This threshold is two orders of magnitude higher than that 
for similar edge emitting organic semiconductor lasers as a consequence of 
higher optical losses in the microcavity structure (500 cm.sup.-1), and a 
short gain length (500 nm). The Alq.sub.3 :DCM material gain at threshold 
in OVCSELs is estimated to be g.sub.TH =500 cm.sup.-1, which is comparable 
to the internal gain in InGaAs/GaAs quantum well structures. 
The subject invention as disclosed herein may be used in conjunction with 
co-pending applications: "High Reliability, High Efficiency, Integratable 
Organic Light Emitting Devices and Methods of Producing Same", Ser. No. 
08/774,119 (filed Dec. 23, 1996), for which the Issue Fee was paid on Sep. 
23, 1999; "Novel Materials for Multicolor Light Emitting Diodes", Ser. No. 
08/850,264 (filed May 2, 1997) for which the Issue Fee was paid on Jan. 
21, 2000; "Electron Transporting and Light Emitting Layers Based on 
Organic Free Radicals", Ser. No. 08/774,120 (filed Dec. 23, 1996), now 
U.S. Pat. No. 5,811,833; "Multicolor Display Devices", Ser. No. 08/772,333 
(filed Dec. 23, 1996), now U.S. Pat. No. 6,013,982; "Red-Emitting Organic 
Light Emitting Devices (OLED's)", Ser. No. 08/774,087 (filed Dec. 23, 
1996), for which the Issue Fee was paid on Jul. 21, 1999; "Driving Circuit 
For Stacked Organic Light Emitting Devices", Ser. No. 08/792,050 (filed 
Feb. 3, 1997), now U.S. Pat No. 5,757,139; "High Efficiency Organic Light 
Emitting Device Structures", Ser. No. 08/772,332 (filed Dec. 23, 1996), 
now U.S. Pat. No. 5,834,893; "Vacuum Deposited, Non-Polymeric Flexible 
Organic Light Emitting Devices", Ser. No. 08/789,319 (filed Jan. 23, 
1997), now U.S. Pat. No. 5,844,363; "Displays Having Mesa Pixel 
Configuration", Ser. No. 08/794,595 (filed Feb. 3, 1997); "Stacked Organic 
Light Emitting Devices", Ser. No. 08/792,046 (filed Feb. 3, 1997), now 
U.S. Pat. No. 5,917,280; "High Contrast Transparent Organic Light Emitting 
Device Display", Ser. No. 08/821,380 (filed Mar. 20, 1997), now U.S. Pat. 
No. 5,986,401; "Organic Light Emitting Devices Containing A Metal Complex 
of 5-Hydroxy-Quinoxaline as A Host Material", Ser. No. 08/838,099 (filed 
Apr. 15, 1997), now U.S. Pat. No. 5,861,219; "Light Emitting Devices 
Having High Brightness", Ser. No. 08/844,353 (filed Apr. 19, 1997), which 
has been allowed; "Organic Semiconductor Laser", Ser. No. 08/859,468 
(filed May 19, 1997); "Saturated Full Color Stacked Organic Light Emitting 
Devices", Ser. No. 08/858,994 (filed on May 20, 1997), now U.S. Pat. No. 
5,932,895; "An Organic Light Emitting Device Containing a Hole Injection 
Enhancement Layer", Ser. No. 08/865,491 (filed May 29, 1997), now U.S. 
Pat. No. 5,998,803; "Plasma Treatment of Conductive Layers", 
PCT/US97/10252, (filed Jun. 12, 1997); "Patterning of Thin Films for the 
Fabrication of Organic Multi-color Displays", PCT/US97/10289, (filed Jun. 
12, 1997); "OLEDs Containing Thermally Stable Asymmetric Charge Carrier 
Materials", Ser. No. 08/925 029, filed Sep. 8, 1997; "Light Emitting 
Device with Stack of OLEDS and Phosphor Downconverter", Ser. No. 
08/925,403, (filed Sep. 9, 1997), now U.S. Pat. No. 5,874,803; "An 
Improved Method for Depositing Indium Tin oxide Layers in Organic Light 
Emitting Devices", Ser. No. 08/928,800 (filed Sep. 12, 1997), now U.S. 
Pat. No. 5,981,306; "Azlactone-Related Dopants in the Emissive Layer of an 
Oled" (filed Oct. 9, 1997), for which the issue fee was paid on Jan. 7, 
2000, Ser. No. 08/948,130, "A Highly Transparent Organic Light Emitting 
Device Employing A Non-Metallic Cathode", (filed Nov. 3, 1997), which was 
a provisional application that has now been converted to regular 
application Ser. No. 08/964,863, Attorney Docket No. 10020/40 
(Provisional), "A Highly Transparent Organic Light Emitting Device 
Employing a Non-Metallic Cathode", (filed Nov. 5, 1997), Ser. No. 
08/964,863, Attorney Docket No. 10020/44, "Low Pressure Vapor Phase 
Deposition of Organic Thin Films" (filed Nov. 17, 1997), Ser. No. 
08/972,156, Attorney Docket No. 10020/37, "Method of Fabricating and 
Patterning Oleds", (filed Nov. 24, 1997), Ser. No. 08/977,205, Attorney 
Docket No. 10020/14, "Method for Deposition and Patterning of Organic Thin 
Film", (filed Nov. 24, 1997), now U.S. Pat. No. 5,953,587, Attorney Docket 
No. 10020/25 and "OLEDS Doped With Phosphorescent Compounds" (filed Dec. 
1, 1997), Ser. No. 08/980,986, Attorney Docket No. 10020/47; each 
co-pending application being incorporated herein by reference in its 
entirety. The subject invention may also be used in conjunction with the 
subject matter of each of co-pending U.S. patent application Ser. Nos. 
08/354,674, now U.S. Pat. No. 5,707,745, 08/613,207, now U.S. Pat. No. 
5,703,436, 08/632,322, now U.S. Pat. No. 5,757,026, and 08/693,359 and 
provisional patent application Ser. Nos. 60/010,013, which was converted 
to a regular U.S. application and is now U.S. Pat. No. 5,986,268, 
60/024,001, which was converted to a regular U.S. application and is now 
U.S. Pat. No. 5,844,363, 60/025,501, which was converted to a regular U.S. 
application Ser. No. 08/844,353, which has been allowed, 60/046,061 which 
was converted to a regular U.S. application Ser. No. 08/859,468 and 
60/053,176, which was converted to a regular U.S. application Ser. No. 
09/010,594, each of which is also incorporated herein by reference in its 
entirety. 
The present invention provides for optical semiconductor lasers with 
desired properties such as narrow bandwidth emission, the minimal use of 
active organic materials, and the facilitation of wavelength tuning and 
electrical pumping. The vertical-cavity surface-emitting structures of the 
present invention represent the first known successful demonstration of 
lasing action in a small molecular weight organic semiconductor 
microcavity structure associated with a clear threshold in the output 
power, a well defined laser beam, cavity modes, and spectral line 
narrowing of emission above threshold to less than 1 .ANG.. Those with 
skill in the art may recognize various modifications to the embodiments of 
the invention described and illustrated herein. Such modifications are 
meant to be covered by the spirit and scope of the appended claims.