Heat dissipating device for laser diodes

A heat dissipating device and method for dissipating waste heat produced by a solid state device, which includes (a) a solid state device and (b) a heat sink for dissipating waste heat produced by the solid state device which includes a base member being in thermal contact with the solid state device and a plurality of elongated heat conducting elements extending outwardly from the base member.

FIELD OF THE INVENTION 
This invention relates to an apparatus and process for dissipating waste 
heat produced by a solid state device, which includes (a) a solid state 
device, and (b) a heat sink for dissipating waste heat produced by the 
solid state device, which includes a base member being in thermal contact 
with the solid state device and a plurality of elongated heat conducting 
elements extending outwardly from the base member. 
BACKGROUND OF THE INVENTION 
A laser is a device which has the ability to produce monochromatic, 
coherent light through the stimulated emission of photons from atoms, 
molecules or ions of an active medium which have typically been excited 
from a ground state to a higher energy level by an input of energy. Such a 
device contains an optical cavity or resonator which is defined by highly 
reflecting surfaces which form a closed round trip path for light, and the 
active medium is contained within the optical cavity. 
If a population inversion is created by excitation of the active medium, 
the spontaneous emission of a photon from an excited atom, molecule or ion 
undergoing transition to a lower energy state can stimulate the emission 
of photons of substantially identical energy from other excited atoms, 
molecules or ions. As a consequence, the initial photon creates a cascade 
of photons between the reflecting surfaces of the optical cavity which are 
of substantially identical energy and exactly in phase. A portion of this 
cascade of photons is then discharged out of the optical cavity, for 
example, by transmission through one or more of the reflecting surfaces of 
the cavity. These discharged photons constitute the laser output. 
Excitation of the active medium of a laser can be accomplished by a variety 
of methods. However, the most common methods are optical pumping, use of 
an electrical discharge, and passage of an electric current through the 
p-n junction of a semiconductor laser. Semiconductor lasers contain a p-n 
junction which forms a diode, and this junction functions as the active 
medium of the laser. Such devices are also referred to as laser diodes. 
The efficiency of such lasers in converting electrical power to output 
radiation is relatively high, and for example, can be in excess of 40 
percent. 
In order to effect optical pumping, the photons delivered to the lasant 
material from a radiant source must be of a very precise character. In 
particular, the pumping radiation must be of a wavelength which is 
absorbed by the lasant material to produce the required population 
inversion. 
The flow of current through a laser diode perturbs the electron population 
in the valence and conduction bands. The energy gap between the lowest 
empty level in the valence band and the lowest filled level in the 
conduction band is altered. The net effect is that the output wavelength 
is dependent on the driving current. The wavelength increases with 
increasing drive current. For gallium aluminum arsenide laser diodes, the 
rate of increase is typically 0.025 nm/mA. 
The output wavelength is highly dependent on the detailed electronic 
distribution of the valence and conduction bands. Consequently, output 
wavelength is a function of the temperature of the junction. The emitted 
wavelength increases if the temperature of the junction is increased. 
Typically the emission wavelength changes by 0.3 to 0.4 nanometers per 
degree centigrade. Clearly, if a stable output wavelength is required, the 
temperature of the laser diode must be maintained at a constant level. 
This is usually achieved by using a small thermoelectric cooler unit, a 
thermocouple sensor and a feedback circuit. 
The gain of any lasing medium is a function of the population inversion 
ratio. This is actually a ratio of the perturbed population distribution 
to the equilibrium (Boltzmann) distribution. As the temperature of a laser 
diode junction rises, the natural Boltzman population distribution of the 
electrons changes and even more electrons are required in the conduction 
band to achieve the same effective population inversion. Therefore, for a 
fixed driving current, increasing the temperature of the laser diode will 
normally decrease its output power. 
Laser diode lifetimes in excess of 50,000 hours are not uncommon. However, 
there are certain factors which can have a drastic effect on this. Both 
high device temperature and sudden current spikes can be fatal to laser 
diodes. 
Device failure can be either sudden and catastrophic, or a gradual 
degradation of performance. The gradual degradation process can be due to 
the accumulation of crystalline flaws in the active junction region. These 
can be small or large, but all have their origin as missing atoms or extra 
(interstitial) atoms in the lattice. At these so-called lattice defects, 
there is a discontinuity in the band structure which can allow electrons 
to "leak" from the conduction band down to the valence band without 
emission of a photon. The excess energy is instead released 
non-radiatively as vibrational energy of the lattice. Continual driving of 
a laser diode near its damage threshold, sudden spikes in the driving 
current, and failure to maintain a reasonable junction temperature, can 
all lead to an increase in the number and size of the lattice defects in 
the junction. 
The temperature of a laser diode rises above ambient temperature during 
normal operation for two reasons. Firstly, the semiconductor is heated by 
simple resistive heating. Secondly, the internal photon flux may be 
reabsorbed, particularly by impurities. Clearly, to prolong the life of a 
laser diode it is advantageous to cool the diode in some way. 
Device failure can also result from degradation of the output facet. This 
can be sudden or gradual. It is caused by thermal effects, sometimes in 
conjunction with thermal oxidation. Large spikes in the driving current 
can produce bursts of heat which exceed the heat dissipation capacity of 
the device. This may cause fatal damage or fractures to the output facet. 
It is therefore very important to control the temperature of diode lasers 
since: (1) a diode laser generates an enormous amount of waste heat per 
unit volume and temperature significantly affects, alters and changes the 
characteristics of laser diodes by changing the wavelength of the output 
radiation of laser diode pumps; (2) the lifetime of a laser diode is a 
function of its temperature; (3) the lifetime of a laser diode can be 
decreased significantly in response to a significant rise in temperature; 
and (4) the power output of a laser diode at a constant drive current is a 
function of temperature, and will usually increase as the temperature is 
lowered. 
It is therefore desirable to provide an improved heat removal process and 
device for removing waste heat from laser diodes, which overcomes most if 
not all of the aforementioned problems. 
SUMMARY OF THE INVENTION 
An embodiment of the instant invention includes an apparatus for 
dissipating waste heat, comprising: (a) a solid state device; and (b) a 
heat sink including a base member being in thermal contact with said solid 
state device and a plurality of elongated heat-conducting elements 
extending outwardly from said base member. 
Another embodiment of the instant invention includes an apparatus for 
dissipating waste heat, comprising: (a) a laser diode for generating laser 
light; and (b) a heat sink including a base member being in thermal 
contact with said laser diode and a plurality of elongated heat-conducting 
elements extending outwardly from said base member. 
An embodiment of the instant invention also includes an optically pumped 
laser, comprising: (a) solid-state component means for generating laser 
light along an optical path, said solid-state component means including 
solid-state optical pumping means for generating optical pumping radiation 
at a preselected wavelength and a lasant member comprising a solid lasant 
material for receiving said radiation from said optical pumping means and 
emitting laser light; and (b) heat removal means for removing heat from 
said optical pumping means wherein said heat removal means comprises a 
base member in thermal contact with said optical pumping means, and a 
plurality of elongated heat-conducting elements extending outwardly from 
said base. 
The instant invention also includes a method of dissipating waste heat 
produced by a laser diode, comprising: (a) generating laser light from a 
laser diode while simultaneously producing waste heat; (b) conveying waste 
heat generated by said laser diode away therefrom with a heat sink which 
comprises a base member in thermal contact with said laser diode, and a 
plurality of elongated heat-conducting elements extending outwardly from 
said base; and (c) circulating air about said plurality of elongated 
heat-conducting elements of said heat sink whereby heat is transferred 
from said heat-conducting elements to said circulating air. 
An object of the invention is to provide a solid-state laser and process 
that is highly efficient in both optical pumping and in heat removal. 
A further object is to provide a portable and durable optically pumped 
laser that is simple in construction, easy to install and maintain, and 
that will not lose its cooling or operating properties with age.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
While this invention is susceptible of embodiments in many forms, there is 
shown in FIGS. 1-4 one embodiment suitable for use in the practice of this 
invention, with the understanding that the present disclosure is not 
intended to limit the invention to the embodiment illustrated. 
Referring to FIG. 1, a heat dissipating device 10 is shown. The heat 
dissipating device 10 consists of an elongated heat sink 12, having a base 
14 at one end and a plurality of elongated thermally conductive members or 
pins 16 at the other end of base 14. The base 14 is in thermal contact 
with a solid-state optical pumping means for generating optical pumping 
radiation 18. The optical pumping means 18 can be a laser diode, laser 
diode array, light-emitting diode, light-emitting diode array, and 
equivalents thereof. A preferred solid-state optical pumping means for 
generating optical pumping radiation is a laser diode, hereafter referred 
to as 18. Light from laser diode 18 is guided by lens 20 into lasant 
material 22. 
The laser diode 18 output radiation should substantially match the desired 
absorption band of lasant material 22. For Nd:YAG as the lasant material 
this wavelength would preferably be at about 808 nm. If lasant materials 
other than Nd:YAG are used, then appropriate semiconductor materials, 
compositions, laser diode structures, or operating conditions must be 
chosen so that the laser diode output meets the above wavelength criteria. 
In the optically pumped laser of FIG. 1, laser diode 18 emits light at a 
wavelength at about 808 nm, assuming the absorption peak of the lasant 
material 22 is at about 808 nm. As is known to those skilled in the art, 
the absorption peak of the lasant material can vary from sample to sample. 
Accordingly, the above wavelength value is merely exemplary. 
Heat sink 12 can be passive in character. Heat sink 12 can also include a 
thermoelectric cooler to help maintain laser diode 18 at a constant 
temperature and thereby ensure optimal operation thereof. During operation 
the laser diode 18 will be attached to a suitable power supply. Electrical 
leads from laser diode 18, which are connected to a power supply, are not 
illustrated in FIG. 1. 
Lasant material 22 has a suitable reflective coating on input surface 24 
and is capable of being pumped by the light from laser diode 18. The 
reflective coating on input surface 24 is highly transparent with respect 
to light produced by the laser diode 18 but is highly reflective with 
respect to light produced by the lasing of lasant material 22. The lasant 
material 22 also has an output surface 26. 
Light emitted by the lasing of lasant material 22 from optical pumping 
means 12, is passed through a nonlinear optical material 28 to output 
coupler 30 which has a suitable reflective coating on surface 32 which is 
highly reflective with respect to light emitted by lasant material 22 but 
substantially transparent to frequency-modified light produced by 
nonlinear optical material 28. Nonlinear optical material 28 has an output 
surface 29. Output coupler 30 is configured in such a manner that it 
serves to collimate the output radiation from the laser which passes 
through it. It should be understood, however, that nonlinear optical 
material 28 is not required for the practice of this invention, and merely 
represents a preferred embodiment of this invention. 
Lens 20 serves to focus light from laser diode 18 onto lasant material 22. 
This focusing results in a high pumping intensity and an associated high 
photon to photon conversion efficiency in lasant material 22. Any 
conventional optical means for focusing light can be used in place of lens 
20. For example, a gradient index lens, a ball lens, an aspheric lens or a 
combination of lenses can be utilized. Lens 20 is not essential to the 
operation of this invention, and the use of such focusing means merely 
represents a preferred embodiment. 
Any conventional lasant material 22 can be utilized in the present 
invention, provided that it is capable of being optically pumped by the 
laser diode 18 selected. Suitable lasant materials include, for example, 
materials consisting of neodymium-doped yttrium vanadate (Nd:YVO.sub.4); 
neodymium and/or chromium-doped gadolinium scandium gallium garnet (Nd, 
Cr:GSGG); thulium, holmium and/or erbium-doped yttrium aluminum garnet 
(Tm, Ho, Er:YAG); titanium sapphire (Ti:Al.sub.2 O.sub.3); glassy and 
crystalline host materials which are doped with an active material. Highly 
suitable active materials include, ions of chromium, titanium and the rare 
earth metals. A neodymium-doped YAG is a highly suitable lasant material 
22 for use in combination with laser diode 18 producing light having a 
wavelength of about 808 nm. When pumped with light of this wavelength, the 
neodymium-doped YAG or lasant material 22 can emit light having a 
wavelength of 1,064 nm. The geometric shape of lasant material 22 can vary 
widely. 
Lasant material 22 has a reflective coating on surface 24. This coating is 
conventional in character and is selected so as to transmit as much 
incident pumping radiation from laser diode 18 as possible, while being 
highly reflective with respect to the radiation or light produced by the 
lasing of lasant material 22. 
For a neodymium-doped YAG rod lasant material 22 which is pumped with light 
having a wavelength of 808 nm, the coating on input surface 24 should be 
substantially transparent to 808 nm light and highly reflective with 
respect to light having a wavelength of 1,064 nm. In a preferred 
embodiment, this coating will also be highly reflective of light having a 
wavelength of 532 nm, the second harmonic of the aforementioned 1,064 nm 
light. The wavelength selective mirror which is created by the coating on 
input surface 24 need not be located on the input surface 24 of lasant 
material 22. If desired, this mirror can be located anywhere between laser 
diode 18 and the lasant material 22, and can consist of a coating 
deposited on any suitable substrate. In addition, the mirror can be of any 
suitable shape. 
Light emitted by the lasing of lasant material 22 from optical pumping 
means 18, is passed through nonlinear optical material 28. The nonlinear 
optical material 28 can consist of one or more pieces of the appropriate 
material. By proper orientation of the crystal structure of the nonlinear 
optical material 28 with respect to the incident light produced by lasant 
material 22, the frequency of the incident light can be modified, for 
example, doubled or tripled, by passage through nonlinear optical material 
28. For example, light having a wavelength of 1,064 nm, from a 
neodymium-doped YAG lasant material 22 can be converted to light having a 
wavelength of 532 nm upon passage through nonlinear optical material 28. 
The geometric shape of nonlinear optical material 24 can vary widely. 
Further, any such nonlinear optical component can comprise heating or 
cooling means to control the temperature of the nonlinear optical material 
28 and thereby optimize its performance as a harmonic generator. 
Potassium titanyl phosphate is a preferred nonlinear optical material 28. 
However, any of the many known nonlinear optical materials can be 
utilized, such as, KH.sub.2 PO.sub.4, LiNbO.sub.3, KNbO.sub.3, LiIO.sub.3, 
HIO.sub.3, KB.sub.5 O.sub.8.sup.. 4H.sub.2 O, urea and compounds of the 
formula MTiO(XO.sub.4) where M is selected from the group consisting of K, 
Rb and Tl, and X is selected from the group consisting of P and As. 
As a consequence of the fact that nonlinear optical material 28 is not 100 
percent efficient as a second harmonic generator, light passing through 
this component from lasant material 22 will ordinarily consist of a 
mixture of frequency modified and unmodified light. In the case of 
frequency doubling of light having a wavelength of 1,064 nm from 
neodymium-doped YAG as the lasant material 22, the light passed through 
nonlinear optical material 28 will be a mixture of 1,064 nm and 532 nm 
wavelengths. This mixture of wavelengths is directed to output coupler 30 
which has a reflective coating on surface 32, which is wavelength 
selective. This coating is conventional in character and is selective in 
such a manner that it is substantially transparent to the 532 nm light but 
highly reflective with respect to the 1,064 nm light. Accordingly, 
essentially only frequency doubled light having a wavelength of 532 nm is 
emitted through the output coupler 30. 
The output coupler 30 includes a wavelength selective mirror which is 
created by the coating on surface 32. It need not be of the precise design 
illustrated in FIG. 1, and can be of any conventional form. For example, 
the wavelength selective mirror can be created by a coating on surface 29 
of nonlinear optical material 28. In this event, output coupler 30 could 
be either eliminated or replaced by optical means whose sole purpose is to 
collimate or otherwise modify the output radiation or laser light from the 
lasant material 22. The output coupler 30 can be of any appropriate 
geometric shape. However, the concave shape of the mirror created by the 
coating on surface 32 has the advantage of focusing reflected light, which 
has not been frequency doubled, back onto nonlinear optical material 28, 
through lasant material 22 and onto the coating on input surface 24. As 
set forth above, in a preferred embodiment, this coating on surface 24 is 
highly reflective of both frequency doubled and unmodified light from the 
lasing of lasant material 22. Thus, frequency-unmodified light reflected 
by the coating on surface 32 is partially frequency doubled by passage 
through nonlinear optical material 28, the resulting mixture of 
wavelengths is reflected from the coating on input surface 24 back through 
nonlinear optical material 28 where some of the residual 
frequency-unmodified light is frequency doubled, and the frequency doubled 
light is emitted through output coupler 30. Except for losses, which may 
occur as a result of processes such as interference, reflection, 
scattering, absorption or imperfect coatings, further repetition of this 
series of events results in essentially all of the light produced by the 
lasing of lasant material 22 being frequency doubled and emitted through 
output coupler 30. 
Referring to FIG. 2, there is schematically drawn an optically pumped laser 
which is suitable for the practice of this invention. A portable laser 
head or elongated or tubular housing 40 encloses and houses all of the 
elements of the instant invention therein. The housing 40 includes a rear 
and front section, 42 and 44, respectively. The front section 44 has a 
bore 45 for allowing laser light to be emitted therethrough. The rear 
section 42, can have a twelve-conductor Hirose connector 46 for connecting 
power to the laser diode, thermistor, TE cooler, fan, etc., as discussed 
hereafter. The rear section 42 has three elongated vents 48 around the 
periphery thereof, near edge 50. 
A fan or blower 52 is enclosed, housed and snugly fitted within the rear 
section 42, and can be adhesively attached to an inner portion of rear 
section 42. A screen 54 and attaching means or screw 56 are attached to 
fan 52 within rear section 42, and allows air to be drawn through the 
vents 48 upstream toward the fan 52. The air to be circulated generally 
enters through vents 48 at ambient temperature and escapes through the fan 
52. The fan 52 when energized draws air about the pins 66 of heat sink 58 
for substantially evenly cooling pins 66 and dissipating heat therefrom. 
Moving downstream from rear section 42, is a metallic heat sink 58. 
Preferably, heat sink 58 will be constructed from a metal which has a 
thermal conductivity in excess of about 2 watt/cm. .degree.C. The heat 
sink 58 can have a thermal conductivity of less than about 5.degree. 
C./watt, preferably less than about 1.degree. C./watt, and most preferably 
about 0.4.degree. C./watt. The metallic heat sink 58 includes a base 
member 60, with a circular flat side 62 and flange 64, and opposite the 
flat side 62, is attached a plurality of thermally conductive elongated 
members or pins 66. 
The pins 66 are perpendicular to flat side 62. As will be appreciated by 
those skilled in the art, the geometric shape of the heat sink 58, as well 
as the base 60, flat side 62, flange 64 and pins 66 can vary. The above 
geometric shapes are merely exemplary. 
The pins 66 provide a large surface area in a relatively small area within 
the rear section 42, which improves the air cooling of the pins 66 and the 
channeling and dissipating of heat away therefrom. The flat side 62 of 
base 60 has a plurality of fastening bores 68 and a conduit bore 70. The 
conduit bore 70 allows passage of leads or wires near or downstream of the 
base 60 to be passed through the metallic heat sink 58 upstream to the 
connector 46. 
The outer diameter of rear section 42 and flange 64 are the same, so that 
when the housing 40 is fully assembled, it appears as a unitary device. 
Once assembled, the edge 50 of the rear section 42 touches, abuts, and can 
be adhesively bonded to a lower portion 65 of flange 64. Thus, when fan 52 
is operating, the air is drawn by fan 52 only through vents 48. 
Referring to FIG. 4, the plurality of thermally conductive elongated 
members or pins 66, include nine rings of pins, designated as a, b, c, d, 
e, f, g, h, and i, respectively, each subsequent ring having a smaller 
diameter than the preceding ring. The pins 66 can be of any geometric 
shape. Preferably, the pins 66 are substantially rod shaped and of uniform 
length and diameter. The ratio of the surface area of the length of each 
pin 66, which includes the external boundary or circumference from the 
base 60 to and excluding the tip of each pin, to the circular 
cross-sectional area of each pin is at least 2:1. The preferred ratio of 
surface area of the length to circular cross-sectional area of each pin is 
at least 10:1, and most preferred at least 25:1. 
Ring a includes 36 pins each separated by an angle of 10.degree.. Offset 
from ring a is b, which includes 35 pins each separated by an angle of 
10.degree.. One pin is omitted for conduit bore 70. Rings c and d each 
include 30 pins, and each pin in each ring is separated by an angle of 
12.degree.. Ring c is offset from ring d. Ring e includes 20 pins, and 
each pin is separated by an angle of 18.degree.. Ring f includes 15 pins, 
and each pin is separated by an angle of 24.degree.. Ring g includes 12 
pins, and each pin is separated by an angle of 30.degree.. Ring h includes 
4 pins, and each pin is separated by an angle of 90.degree.. And ring i 
includes one pin in the center of base 60. It should be understood, 
however, that the geometric shape of each pin, the ratio of the surface 
area of the length to circular cross-sectional area of each pin, the 
number of pins in each ring and the angle of separation of each pin in 
each ring can very widely, and the specific structure illustrated in FIG. 
4 represents a preferred embodiment of this invention. 
Referring to FIG. 2, in a preferred embodiment the fan 52 is energized to 
circulate and draw air upstream from the vents 48 to and through the 
plurality of thermally conductive pins 66 in a substantially homogenous 
and uninterrupted flow, and to and through fan 52. This provides cold air 
to be drawn in proximity to the portion of the pins 66 near the flange 64 
first, which is the hottest portion, and then upstream along pins 66 to 
and through fan 52. The fan 52 can also be used to blow air downstream to 
and through the pins 66 and out vents 48 to maximize the air flow and 
temperature difference along the pins 66. The rings a, b, c, d, e, f, g, 
h, and i are positioned so as to force the air to flow uniformly about, 
and to cool each pin independently, thereby lowering the temperature of 
heat sink 58, which of course helps to keep the laser diode 88 which is in 
thermal contact therewith, at a stable temperature. The fan 52 is normally 
on during operation. The vents 48 allow air to circulate about and air 
cool pins 66, even if the fan 52 is not energized. 
Referring to FIG. 3, downstream of metallic heat sink 58 is a 
thermo-electric (TE) heater/cooler 72, a spreader 80, a laser diode 88 and 
a resonator housing 120. As illustrated in FIG. 3, the TE cooler 72 has a 
lower section, a hot junction or plate 74, which is thermally conductive 
and electrically insulative, a cold junction or platform 76 thereabove, 
and legs 78 attaching platform 76 to plate 74. 
The TE cooler 72 is utilized to remove waste heat from the laser diode 87 
or a solid state device and be monitored using conventional temperature 
sensors, such as thermocouples, thermistors, etc. When the temperature 
deviates from a desired value, a voltage is produced in the sensing 
circuit. The sign of this voltage indicates whether the temperature is 
warmer or colder than the preset null point. Current is automatically 
supplied in the direction necessary to correct the temperature drift. The 
TE cooler 72 is in thermal contact with heat sink 58 to dissipate and 
absorb heat in order to maintain the required temperature. 
Generally, in a thermoelectric cooler, semiconductor materials with 
dissimilar characteristics are connected electrically in series and 
thermally in parallel, so that two junctions are created. 
The legs 78 are made of alternating N and P-type semiconductor materials, 
and are so named because either they have more electrons than necessary to 
complete a perfect molecular lattice structure (N-type) or not enough 
electrons to complete a lattice structure (P-type). The extra electrons in 
the N-type material and the holes left in the P-type material are called 
"carriers" and they are the agents that move the heat energy from the 
platform 76 or cold junction to the plate 74 or hot junction. 
Referring to FIG. 3, the plate 74 can be made of a ceramic material, such 
as beryllium oxide, alumina (Al.sub.2 O.sub.3), or boron nitride, 
preferably beryllium oxide due to its superior thermal conductivity. The 
plate 74 has a larger surface area than the platform 76, and such plate 74 
dissipates heat toward heat sink 58, not only in the area directly below 
platform 76, but also in the area (not directly below platform 76) away 
from platform 76. 
A spreader 80 is in direct thermal contact with, and attached to and above 
platform 76. The spreader 80 is both thermally and electrically 
conductive, and for example can be made of copper with a gold plating. The 
spreader 80 has top, bottom and inclined surface 82, 84, and 85, 
respectively. The top surface 82 can have a bore for fastening a laser 
diode thereto. 
A submount-packaged laser diode 87, such as, but not limited to, Sony Model 
SLD 304B or a Spectra Diode Laboratories Model SDL 2460-C is attached 
above and fastened to the top surface 82 of spreader 80, as illustrated in 
FIG. 3. The submount package 87 includes a mounting block or heat sink 86 
and a laser diode 88, with a fastening means or screw 90 attaching the 
mounting block 86 to the top surface 82 of the spreader 80. As is known to 
those skilled in the art, the type of laser diode package and the 
geometric shape of all of the devices described herein can vary. 
Accordingly, the particular package 87 described herein is merely 
exemplary. 
As illustrated in FIG. 3, power is applied to laser diode 88 by ground lead 
94 and positive lead 92, which is attached to first and second inner posts 
93 and 95, respectively. 
A temperature sensing means, such as a thermistor or thermocouple 96 can be 
attached to platform 76, as illustrated in FIG. 3, to sense the 
temperature. The thermistor 96 has a first lead 98 and second lead 100 
each of which is electrically connected to a third and fourth inner post 
99 and 101, respectively. A fifth and sixth inner post 102 and 103 are 
included for use with an optical photo diode to monitor the power output 
of laser diode 88, which is not illustrated in FIG. 3. The inner posts 93, 
95, 99, 101, 102, and 103 are electrically connected to first, second, 
third, fourth, fifth, and sixth outer posts 104, 105, 106, 107, 108, and 
109, respectively by electrically conductive leads on the top surface of 
plate 74, (see FIGS. 2 and 3). It should be understood, however, that such 
leads could be within or on the bottom of plate 74, and that the placement 
of such leads on the top surface of plate 74 merely represents a preferred 
position. Thus, plate 74 is also utilized as a circuit board. Seventh and 
eighth outer post 110 and 111, are electrically attached by conductive 
leads on the top surface of plate 74 to the TE cooler 72 and are utilized 
for applying power to the TE cooler 72. 
Although not illustrated in the figures, the first, second, third, fourth, 
fifth, sixth, seventh, and eighth outer posts 104, 105, 106, 107, 108, 
109, 110, and 111, are electrically connected by wires or leads through at 
least one conduit bore 70 of metallic heat sink 58 to the connector 46. 
The fan 52 leads would also be connected to connector 46. 
Enveloping the laser diode 88 is a cover 112, which can be metallic, 
although any other suitable material, such as plastic, can be used. The 
cover 112 includes a transparent window 114 through which output radiation 
from laser diode 88 is transmitted. An inert gas, such as argon or 
nitrogen, can be enclosed in cover 112. If cover 112 is metallic, an 
insulating layer on ring 116 can be deposited on plate 74 so as not to 
short the electrical connections between the inner and outer posts. Plate 
74 has a plurality of bores for connecting or fastening the plate 74 to 
the heat sink 58. 
Downstream of the laser diode 88 and heat sink 58 inserted snugly within 
front section 44, is a resonator housing 120. The resonator housing 120 
includes a center bore 122 and fastening bores 124. The fastening bores 
124 provide a means for fastening or screwing the resonator housing 120 
through plate 74 to heat sink 58. Referring to FIG. 1, the elements within 
the dashed line designated as 120 can be held securely within the 
resonator housing 120 center bore 122. 
During operation, waste heat is produced by the laser diode 88 when such 
laser 88 is operated to produce optical pumping radiation for lasant 
material 22. This waste heat is efficiently conveyed away from the laser 
diode 88. 
Since heat flow can be impeded at the junction between materials, the lower 
the number of junctions connecting a laser diode to a heat sink, the more 
efficient the heat can be channelled and dissipated away from such laser 
diode. As illustrated in FIGS. 2 and 3, the heat dissipating device 10 
includes only four junctions 128, 130, 132 and 134, which only slightly 
interfere with this channelling. The laser/mounting block junction 128 is 
where the laser diode 88 interfaces with the mounting block 86 of package 
87. The mounting block/spreader junction 130 is the area where the 
mounting block 86 contacts the top surface 82 of the spreader 80. The 
third junction is the spreader/TE cooler junction 132 where the bottom 
surface 84 of spreader 80 and the top surface of the platform 76 of TE 
cooler 72 meet or interface. The fourth junction is the TE cooler/heat 
sink junction 134, where the bottom surface of plate 74 and the flat side 
62 of the metallic heat sink 58 meet or interface. 
The geometric shape and surface area of each of the aforementioned 
junctions thermally contact and closely match that of the adjoining 
elements. Accordingly, the geometry of the laser/mounting block junction 
128 closely matches and is substantially the same as the geometric shape 
of the laser diode 88 and mounting block 86 at that junction 128. 
Similarly, the rectangular shape and surface area of the mounting 
block/spreader junction 130, closely matches the geometric shape and 
surface area of the mounting block 86 and top surface 82 of spreader 80. 
In a similar fashion, the rectangular spreader/TE cooler junction 132, 
closely matches the geometric shape and surface area of the bottom surface 
84 of spreader 80, and the platform 76 of TE cooler 72, and the annular 
shape and surface area of the TE cooler/heat sink junction 134, closely 
matches the geometric shape and surface area of the plate 74 and the flat 
side 62 of the heat sink 58. It should be understood, however, that any 
geometric shape for each junction can be utilized as long as the surface 
area and geometry of the adjoining elements and junction are closely 
matched to allow maximum heat dissipation. 
Waste heat is channeled and spread out from laser diode 88, upstream 
through junctions 128, 130, 132 and 134 to heat sink 58. The surface area 
of each subsequent junction is larger than the one preceding, for an 
enhanced and even heat spread from junctions 128, 130, 132 and 134 to the 
heat sink 58. 
The efficiency of waste heat removal is further attributable to the large 
surface area of the plurality of thermally conductive elongated members or 
pins 66. The high number of pins 66 maximizes and utilizes a relatively 
small volume in housing 40 for air cooling the heat sink 58. Such a 
condensed and small volume allows the housing 40 (or laser head) to be 
portable, light weight and durable. 
The pin design comprising rings a-i, allows air to evenly circulate in an 
efficient manner, whether the fan 52 is energized or not. When the fan 52 
is energized, air is substantially circulated homogenously and evenly 
about the pins 66. The rings a-i are designed to channel and deflect the 
air in such a pattern through pins 66 that maximizes the deflecting of air 
through the pins 66. More particularly, the pins 66 are configured to 
allow the air to be drawn in through the vents 48, through the pins 66 in 
an inwardly direction from ring a to ring i, then upstream and through fan 
52. The design of pins 66 provides a substantially complete, full and 
virtually uniform air distribution and circulation for efficient and 
effective thermal dissipation. 
The front section 44 of the housing 40 has the same outer diameter as the 
flange 64, so that when the housing 40 is fully assembled, it appears as a 
unitary and portable laser head, which is energized by a power supply 
through a cable connected to connector 46. 
In an alternative embodiment not shown in the drawings, the laser diode 18 
of the instant invention can be replaced with any solid state or 
semiconductor device, such as, but not limited to an infra red detector or 
charge coupled device. It will be appreciated that the term semiconductor 
is generally synonymous with the term solid state, and as used herein 
refers to a material in which an electric current is carried by electrons 
or holes and is characterized by a bandgap which is the difference in 
energy between an electron in the material's normally filled valence band 
and an electron in the conduction band of the material. Such materials 
have a relatively low electrical conductivity which can be increased by 
several orders of magnitude by doping with electrically active impurities. 
Conventional semiconductors include silicon, germanium and various 
combinations of elements from Groups III and V of the Periodic Table such 
as InAs, InP, GaP, GaAs, AlAs, AlGaAs, InGaAs, InGaAsP, InGaP and InGaAlP. 
A tabulation of some of the more common semiconductors and their general 
properties is set forth at pages E-102 through E-105 of the Handbook of 
Chemistry and Physics, 68th Ed., CRC Press, Inc., Boca Raton, Fla. 
(1987-1988). In such an embodiment, an apparatus for dissipating waste 
heat is disclosed, which comprises: (a) a solid state device; and (b) a 
heat sink 12 including a base member 14 being in thermal contact with the 
solid state device and a plurality of elongated heat-conducting elements 
66 extending outwardly from the base member 14. 
Although only one embodiment of this invention has been shown and 
described, it is to be understood that various modifications and 
substitutions, as well as rearrangements and combinations of the 
proceeding embodiment, can be made by those skilled in the art without 
departing from the novel spirit and scope of this invention.