Ex Parte Hu et al

Board of Patent Appeals and Interferences

Nov 24, 2009

10661832 (B.P.A.I. Nov. 24, 2009)

UNITED STATES PATENT AND TRADEMARK OFFICE
_____________

BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
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Ex parte QING HU and BENJAMIN S. WILLIAMS
_____________

Appeal 2009-002951
Application 10/661,832
Technology Center 2800
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Decided: November 24, 2009
_______________

Before KENNETH W. HAIRSTON, ROBERT E. NAPPI, and THOMAS S.
HAHN, Administrative Patent Judges.

NAPPI, Administrative Patent Judge.

DECISION ON APPEAL
Appeal 2009-002951
Application 10/661,832

This is a decision on appeal under 35 U.S.C. § 6(b) of the rejection of
claims 1 through 18.
We affirm.
INVENTION
The invention is directed to waveguides that can be used for confining
lasing modes in the THz range. See paragraphs 0008-0010 of Appellants’
Specification. Claim 1 is reproduced below:
1. A quantum cascade laser, comprising:
an active region for generating lasing radiation in a frequency
range of about 1 to about 10 Terahertz, and
a waveguide formed of an upper metallic layer and a lower
metallic layer, each layer being disposed on a surface of said active
region so as to confine selected modes of said lasing radiation within
said active region.

REFERENCES
Kneissl US 2004/0105471 A1 Jun. 3, 2004

Karl Unterrainer et al. (Unterrainer), “Quantum Cascade Lasers with
Double Metal-Semiconductor Waveguide Resonators,” American Institute
of Physics, Applied Physics Letters, vol. 80, no. 17, 3060-3062 (April 29,
2002).

Bin Xu et al. (Xu), “Electrically Pumped Tunable Terahertz Emitter
Based on Intersubband Transition,” American Institute of Physics, Applied
Physics Letters, vol.71, no. 4, 440-442 (July 28, 1997).

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REJECTIONS AT ISSUE
The Examiner has rejected claims 1 through 6 and 8 through 18, under
35 U.S.C. § 103(a) as being unpatentable over Unterrainer in view of Xu.
The Examiner’s rejection is on pages 4 through 91 of the Answer.2
The Examiner has rejected claim 7 under 35 U.S.C. § 103(a) as being
unpatentable over Unterrainer in view of Xu and Kneissl. The Examiner’s
rejection is on page 9 of the Answer.
ISSUES
Claims 1 through 6, and 8
Appellants argue on pages 4 through 7 of the Brief3 that the
Examiner’s rejection of claims 1 through 6 and 8 is in error. Appellants
argue on page 5 of the Brief that Unterrainer’s teachings apply to a shorter
wavelength than that recited in claim 1. Appellants also argue that
Unterrainer and Xu teach away from using the double sided wave guides as
recited in claim 1. Appellants argue that one skilled in art would not be
motivated to combine the teachings of Xu and Unterrainer .
Thus, Appellants’ contentions directed to the rejection of claim 14
present us with two issues:

1 We note that the Examiner relies upon different rationale to reject claims 1,
4, 6, 9 through 14, and 18 on page 7 through 9 of the Answer than on pages
4 through 6, but nonetheless rejects the claims over the combined teachings
of Unterrainer and Xu. Further, we note that though claim 14 is not
identified in the statement of the rejection on page 7 of the Answer, the
rationale supporting the rejection on page 9 identifies claim 14 as rejected.
2 Throughout the opinion we refer to the Answer mailed May 1, 2007.
3 Throughout the opinion we refer to the Brief dated December 11, 2006.
4 Appellants’ arguments group claims 1 through 6, and 8. We select claim 1
as representative of the group.
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1) Have Appellants shown that the Examiner erred in determining that
the combined teachings of Unterrainer and Xu teach a laser waveguide that
operates in a frequency range of 1 to 10 Terahertz with the waveguide
formed with an upper and lower metallic layer (double sided metal
waveguide) as recited in claim 1?
2) Have Appellants shown that the Examiner erred in concluding that
one skilled in the art would combine the teachings of Unterrainer and Xu?

Claims 15 and 17
Appellants argue that the rejection of these claims is in error on page
8 of the Brief. Appellants’ arguments assert that claim 15 recites that the
quantum cascade laser operates in a frequency range of about 1THz to about
10THz, and has a waveguide formed with an upper and lower metallic layer.
Thus, Appellants’ arguments directed to these claims present us with the
same issue as the first issue discussed above with respect to claim 1.

Claims 1, 4, 6, and 9 through 14
Appellants argue that the rejection of these claims is in error on pages
8 and 9 of the Brief. Appellants’ arguments directed to these claims present
us with the same issues discussed above with respect to claim 1.
Claim 18
Appellants argue on page 9 of the Brief, that the rejection of claim 18
is error. Appellants argue that claim 18 recites a Terahertz amplifier
operating in the range between 1 THz to about 10 THz. Appellants argue
that for the reasons discussed above with respect to claim 1, the combined
teachings of Unterrainer and Xu do not teach or suggest a laser which
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operates in a frequency range of 1 to 10 Terahertz and has a waveguide
formed with an upper and lower metallic layer (double sided metal
waveguide).
Thus, Appellants’ arguments directed to claim 18 present us with the
same issue as the first issue discussed above with respect to claim 1.

Claim 7
Appellants argue that the rejection of this claim is in error on pages 9
and 10 of the Brief. Appellants’ arguments directed to these claims present
us with the same issues discussed above with respect to claim 1.
We note that Appellants also argue that the additional teaching of
Kneissl does not make up for the deficiencies in the rejection of claim 1.
We do not reach the issues raised by this argument because as discussed
infra our holding with respect to the rejection of claim 1 is dispositive of any
issues raised by these arguments.

PRINCIPLES OF LAW
Appellant has the burden, when on appeal to the Board, to
demonstrate error in the Examiner’s position. See In re Kahn, 441 F.3d 977,
985-86 (Fed. Cir. 2006). The Examiner bears the initial burden of
presenting a prima facie case of obviousness, and Appellant has the burden
of presenting a rebuttal to the prima facie case. In re Oetiker, 977 F.2d
1443, 1445 (Fed. Cir. 1992).
“‘A reference may be said to teach away when a person of ordinary
skill, upon reading the reference, would be discouraged from following the
path set out in the reference, or would be led in a direction divergent from
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the path that was taken by the applicant.’” Ricoh Co., Ltd. v. Quanta
Computer, Inc., 550 F.3d 1325, 1332 (Fed. Cir. 2008) (quoting Kahn, 441
F.3d at 990). A reference does not teach away if it merely expresses a
general preference for an alternative invention from amongst options
available to the ordinarily skilled artisan, and the reference does not discredit
or discourage investigation into the invention claimed. In re Fulton, 391
F.3d 1195, 1201 (Fed. Cir. 2004).
On the issue of obviousness, the Supreme Court has stated that “the
obviousness analysis cannot be confined by a formalistic conception of the
words teaching, suggestion, and motivation.” KSR Int’l Co. v. Teleflex Inc.,
550 U.S. 398, 419 (2007). Further, the Court stated “[t]he combination of
familiar elements according to known methods is likely to be obvious when
it does no more than yield predictable results.” KSR, 550 U.S. at 416.

FINDINGS OF FACT
1. Unterrainer teaches a Quantum Cascade (QC) laser with a double
metal-semiconductor waveguide resonator for operating at
wavelengths of 19, 21, and 24 μm. Further, it is anticipated that the
double metal-semiconductor, will work in wavelengths into the THz
range. Abstract, p. 3060, and p. 3061, col. 2, para. 2.
2. Unterrainer teaches QC lasers with single sided waveguides, for
which free carrier absorption contributes to losses and that a solution
to the problem is to use a double metal semiconductor waveguide.
P. 3060, col. 1, para. 3 to col. 2 para 1.
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3. Unterrainer teaches that double metal waveguides and the single
metal waveguide have almost equivalent performance, and that at
increased wavelengths the double metal waveguide has better
performance. P. 3061, col. 2, paras. 1 and 2.
4. Unterrainer also identifies that at low currents the light output of the
double metal waveguide is higher than the single sided waveguide.
P. 3062, col. 1, para. 1.
5. Unterrainer identifies that the double metal wave guide exhibits a
slightly lower maximum temperature of operation as shown in
Figure 2. However, this is attributed to poor heat sinking. An
improved bonding process is suggested to improve the heat sinking
and resolve the temperature related problems. P. 3061, col. 2, para.
2, p. 3062 col. 1, para. 1.
6. Xu teaches that the terahertz (THz) frequency range 1-10 THz or 30-
300 μm is underdeveloped and should be utilized. P. 440, para 1.

ANALYSIS
Claims 1 through 6, and 8
First issue:
Appellants have not persuaded us that the Examiner erred in finding
that the combined teachings of Unterrainer and Xu teach a laser which
operates in a frequency range of 1 to 10 Terahertz and has a waveguide
formed with an upper and lower metallic layer. Claim 1 recites a laser
which operates in a frequency range of 1 to 10 Terahertz and has a
waveguide formed with an upper and lower metallic layer (double sided
metal waveguide). The Examiner has found that Unterrainer teaches a laser
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with a waveguide with an upper and lower metallic layer. Answer 4.
Further, the Examiner finds that Unterrainer’s laser generates THz radiation,
but not that the emitted radiation is in the range of 1 to 10 THz. Answer 4,
5. The Examiner finds that Xu teaches use of a laser which radiates in the 1
to 10 THz range and that the skilled artisan would combine the teachings.
Answer 5.
Appellants’ arguments have not persuaded us that the Examiner erred
in finding these facts. Appellants’ arguments on page 5 of the Brief and
pages 3 and 4 of the Reply Brief focus on the upper end of the wavelengths
claimed by Appellants (300 microns), and that these wavelengths are more
than an order of magnitude greater than the wavelengths Unterrainer teaches
as being generated by the double sided metal waveguided laser. The
Examiner provides a comprehensive response on pages 10 and 11 of the
Answer, in which the Examiner finds that Unterrainer discusses operation in
the 24 µm range which is close to the lower end of Appellants claimed range
(which equates to 30-300 µm). Further, the Examiner finds that Unterrainer
teaches a double sided metal waveguide that has improved performance
when used at longer waveguides. Answer 11. We find ample evidence to
support these findings. Facts 3-4. Based upon these findings the Examiner
concludes that the skilled artisan would be motivated to use the extended
wavelengths and have a reasonable expectation of success when combining
the double sided metal waveguide laser with Xu’s teaching of using a laser
at a longer wavelength. Answer 11. We concur with this conclusion by the
Examiner as it is supported by ample evidence.
Appellants’ arguments on pages 5 and 6 of the Brief and page 4 of the
Reply Brief, also focus on the Experimental data depicted in Figure 2 of
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Unterrainer, which shows that the double sided metal waveguide performs
less efficiently. In response, the Examiner states on pages 11 and 12 of the
Answer that while the data in the Figure shows that the single sided metal
waveguide has slightly better characteristics, Figures 2 and 3 in Unterrainer
demonstrate the closeness in performance between single sided metal
waveguides and double sided waveguides. Answer 11. We concur with the
Examiner’s assessment and find that it is supported by the disclosure of
Unterrainer which states “[t]he two waveguiding approaches have therefore
almost equivalent performance.” Unterrainer, p. 3061, col.2, para. 1.
Further, as stated by the Examiner, on pages 12 and 13 of the Answer, even
though Unterrainer in Figures 2 and 3 does identify a slight performance
edge of the single sided metal waveguide, Unterrainer identifies a solution to
improve the performance of the double sided metal waveguide to overcome
the performance disadvantage. Further, Unterrainer teaches that the double
sided metal waveguide has a performance advantage as the wavelengths get
longer (i.e. closer to the region claimed). See Facts 1 and 3 through 5.
Thus, the teachings of Unterrainer, while recognizing some limitations in the
double sided metal waveguide, plainly expresses a preference for use of the
double sided metal waveguide for longer wavelengths. Accordingly,
Appellants’ arguments have not persuaded us that the Examiner erred in
determining that the combined teachings of Unterrainer and Xu teach or
suggest a laser which operates in a frequency range of 1 to 10 Terahertz and
has a waveguide formed with an upper and lower metallic layer (double
sided metal waveguide) as recited in claim 1.
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Second Issue
Appellants have not persuaded us that the Examiner erred in
concluding that one skilled in the art would combine the teachings of
Unterrainer and Xu. Appellants’ arguments on page 6 of the Brief state that
Xu “is not concerned with enhancing the efficiency of mode confinement.”
Appellants conclude that skilled artisans would have no motivation to
consider ways to improve mode confinement and consider Unterrainer’s
teachings which are directed to a different wavelength. Further, Appellants
assert that the skilled artisan would be dissuaded from utilizing the double
sided metal waveguide of Unterrainer as discussed above. We are not
persuaded of error.
In response to the Appellants’ arguments the Examiner states that
though Xu is not concerned with enhancing mode confinement, such a
finding is not required to show that the skilled artisan would combine the
references. We concur with the Examiner that obviousness can be shown if
the combination of familiar elements yields predictable results. KSR, 550
U.S. at 416. The Examiner has found that given Unterrainer’s teachings that
the waveguide would provide improved performance at longer wavelengths,
such as discussed in Xu, a skilled artisan would have a reasonable
expectancy of success. We concur with the Examiner’s conclusion, and, as
discussed supra, we find that the record supports the Examiner’s finding that
Unterrainer teaches a double sided metal waveguide and encourages use of
the waveguide at wavelengths approaching 1 THz (the lower end of the
range taught by Xu and claimed by Appellants). Thus, we find ample
evidence to support the Examiner’s conclusion that using Unterrainer’s
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waveguide in the range taught by Xu would yield a reasonable expectancy of
success (i.e. provide predictable results).
For the aforementioned reasons, the Appellants’ arguments have not
persuaded us of error in the Examiner’s rejection of claim 1 and claims 2
through 6 and 8.

Claims 15 and 17
As discussed above Appellants’ arguments directed to these claims
present us with the same issue as the first issue discussed above with respect
to claim 1. Claim 15, similar to claim 1, recites a laser with an active region
operating in the 1 to 10 THz range, and that the active region is between two
metal layers. As discussed supra, Appellants’ arguments directed to claim 1
have not persuaded us of error in the Examiner’s finding that the
combination of Unterrainer and Xu teaches a laser which operates in a
frequency range of 1 to 10 Terahertz and has a waveguide formed with an
upper and lower metallic layer. Accordingly, we sustain the Examiner’s
rejection of claims 15 and 17 for the reasons discussed with respect to claim
1.

Claims 1, 4, 6, 9 through 13, and 18
As discussed above Appellants’ arguments directed to these claims
present us with same issues discussed above with respect to claim 1.
Accordingly, we sustain the Examiner’s rejection of claims 1, 4, 6, 9 through
13, and 18 for the reasons discussed above with respect to claim 1.

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Claim 18
As discussed above Appellants’ arguments directed to claim 18
present us with the same issue as the first issue discussed above with respect
to claim 1. As discussed supra, Appellants’ arguments directed to claim 1
have not persuaded us of error in the Examiner’s finding that the
combination of Unterrainer and Xu teaches or suggest a laser which operates
in a frequency range of 1 to 10 Terahertz and has a waveguide formed with
an upper and lower metallic layer. Accordingly, we sustain the Examiner’s
rejection of claim 18 for the reasons discussed with respect to claim 1.

Claim 7
As discussed above, Appellants’ arguments directed to this claim
present us with the same issues discussed above with respect to claim 1. As
also discussed above we are not persuaded by Appellants’ arguments
directed to claim 1. We note that Appellants’ additional argument on page
10 of the Brief that the additional teaching of Kneissl does not make up for
the deficiencies in the rejection of claim 1 is not persuasive as we find no
deficiencies in the rejection of claim 1. Accordingly, we sustain the
Examiner’s rejection of claim 7.

CONCLUSION
Appellants have not persuaded us of error in the Examiner’s rejections
of claims 1 through 18.
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ORDER
The decision of the Examiner to reject claims 1 through 18 is
affirmed.
No time period for taking any subsequent action in connection with
this appeal may be extended under 37 C.F.R. § 1.136(a)(1)(iv).

AFFIRMED

ELD

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