Download THz heterodyne receivers using quantum-cascade lasers as local oscillators

THz heterodyne receivers using a quantum
cascade laser as local oscillator
Jian-Rong Gao
SRON Netherlands Institute for Space Research, Utrecht/Groningen, The
Netherlands
Kavli Institute of NanoScience, Delft University of Technology, Delft, The
Netherlands
( Tjeerd Klaassen’s group and Teun Klapwijk’s group)
In collaboration with
MIT /Sandia (USA)
University of Paris VII / Thales/ Cavendish Laboratory, Cambridge
Outline
• Heterodyne technique
• HEB-QCL experiment using a metal-metal waveguide QCL
•Beam patterns of metal-metal waveguide QCLs
•HEB-QCL experiment using surface plasmon mode QCL and the beam
•Requirements of THz QCLs for future space or balloon instruments
• Phase locking and linewidth of two-mode QCLs (if time allows)
Heterodyne detection: principle and advantages
Telescope
Signal LO
IF Spectrum
Local Oscillator
Power
Mixer
IF-amplifier
IF signal (~GHz)
1000
1010
Frequency (GHz)
Power
THz signal
4
8
Frequency (GHz)
back-end
spectrometer
•
mixing a weak RF signal with a strong LO signal
Using a non-linear device, I ∝aV2 or a power-law detector
VS= cos(ωSt+ϕ)
, VLO= cos(ωLot)
IIF ∝ … + VS VLO cos((ωS - ωLo)t +ϕ )
•
high spectral resolution (ν/Δν ≥107)
HEB-QCL experiment using a metal-metal waveguide
MIT QCL at 2.8 THz
25 µm
10 µm
THz Radiation
670 µm
Active region
GaAs/AlGaAs, Metal-metal waveguide
← NbN hot electron bolometer mixer
•2.813 THz, 5~7 K, Max. DC dissipation power is ~1 W
•Max. output power is ~ 1 mW with a Winston cone (measured at MIT). In
QCL-HEB experiment, the power would be less, divergence and window
RF test set-up for QCL-HEB
HEMT
Amplifier
Si lens
HEB
HDPE
window
Mylar
Beam splitter
Eccosorb
295 K / 77 K
Dewar
Amplifier
(295 K)
Mirror
Heat Filter
80 MHz Filter
@ 1.4 GHz
Power
Meter
Mirror
HDPE
THz QCL
Dewar
Fig.2 (J.R. Gao et al)
•Optical loss for QCL ⇔ HEB path: -16.3 dB
Current µ
(A)
300
270 nW
300 nW
330 nW
2000
200
1500
100
fLO=2.8 THz
0
0
1
2
3
Voltage (mV )
4
5
N,rec
Noise temperature
T (K )
Receiver noise temperature of QCL–HEB
25 µm
10 µm
THz Radiation
670 µm
Active region
1000
•A receiver noise temperature of 1400 K at 2.8 THz (6 µm beam splitter)
•extremely stable
•A breakthrough: possible to realize all solid state receiver at any frequencies
• 300 nW → optical loss → 14 µW at QCL ( ~ 1 % of 1 mW can be used)
[1]. J. R. Gao, J. N. Hovenier, Z. Q. Yang, J. J. A. Baselmans, A. Baryshev, M. Hajenius, T. M. Klapwijk, A. J. L. Adam, T. O.
Klaassen. B. S. Williams, S. Kumar, Q. Hu, and J. L. Reno, Appl. Phys. Lett, 2005
[2] H.-W. Hübers et al, Optics Express, 13, 5890(2005).
Beam patterns of metal-metal waveguide
•Subwavelength facet of
a metal-metal QCL
acting as a wire antenna
Laser ”1”
Laser ”2”
W (ì m)
L (ì m)
H (ì m)
! (ì m)
25
25
670
1500
10
10
102.7
109.1
J.L. Adam, I. Kaš alynas, J.N. Hovenier, T.O. Klaassen, J.R. Gao, E.E. Orlova, B.S. Williams, S. Kumar, Q. Hu, and J. L. Reno,
Appl. Phys. Lett. 2006
E.E. Orlova, J.N. Hovenier, T.O. Klaassen, I. Kašalynas, A. J.L. Adam, J.R. Gao, T.M. Klapwijk, B.S. Williams, S. Kumar, Q. Hu,
and J. L. Reno, Phys. Rev. Lett. (2006).
Beam of these surface plasmon QCLs
from Paris group
214!m / 153!m
gion
e
R
ive
Act
1500 !m
Fundamental mode
0.02
!= 100 µm
" = 27%
#= 10 cm-1
active region
12!m
12!m
Mode intensity(arb. units)
0.03
0.01
0.00
undoped GaAs substrate
0
50
0
o
p
m
e
t
a
l
c
o
n
t
a
c
150
Distance (µm)
Top metal contact
T
100
t
Heavily n-doped GaAs channel: botttom contact
H
•Two QCLs
•at 2.84 THz and a few mW output (5 W input)
e
a
v
i
l
y
n
-
d
o
p
e
d
G
a
A
s
c
h
a
n
n
e
l
:
b
o
t
t
t
o
m
c
o
n
t
a
c
t
Beam pattern of the 2.84 THz Surface-plasmon QCL
10 degree offset?
Radiation intensity (normalized)
Beam due to diffraction and antenna effect
1,0
0,8
!5
Measured
Calculated
5.027305"10
Laser "B" ( 214 µm)
!=105.6 µm
Horizontal plane cut
at 10 Degrees
Vertical angle
0,6
(
)2
FLT( # , L , $ , n)
0,4
0,2
0,0
-80 -60 -40 -20 0
20 40
Horizontal angle (Degrees)
60
80
!9
6.985254"10
0
0.1
0.2
0
0.3
0.4
0.5
#
%
214!m / 153!m
• Fraunhofer diffraction for a single slit
• Wire antenna effect
• The wire antenna effect can be removed by
blocking side “facets” of the laser bar
12!m
12!m
gion
e Re
v
i
t
Ac
1500 !m
New receiver noise temperature at 2.84 THz using a
surface plasmon QCL from Paris group
•Surface plasmon QCL + a new HEB designed for high frequencies
• simple optics, thin beam splitter, At 2 K, Trec = 1050 K, (1150 K @ 4.2 K)
•1050 K = 7.7 × hf/k ( “quantum noise”) & a record at such a high frequency
300
M14S-H2
QCL at 2.84 THz
April 12, 2006
250
No LO
optimal,300 nW
over pumped,380 nW
4000
3000
Currentµ( A)
200
150
2000
100
0
1000
1050 K
50
300 nW, TBath=4.2 K
>300 nW, TBath=2 K
0
2
4
6
Voltage (mV)
8
Rec. Noise Temperature (K)
214!m / 153!m
12!m
12!m
gion
e Re
v
i
t
Ac
1500 !m
0
10
M . Hajenius, P. Khosropanah , J.N. Hovenier, J.R. Gao, T.M . Klapwijk, S. Dhillon, S. Barbieri, P. Filloux, C. Sirtori, D.A. Ritchie
and H.E. Beere, ISSTT 2006, in Paris, France
The importance of the new data
DSB Noise Temperature [K]
•good prospect: HEB mixers may remain below 10 × hf/k, at f > 3 THz
Phonon cooled NbN
NbTiN
DLR/MSPU
CfA
CTH
KOSMA
UMass
CfA
MSPU
NICT
IRAM
SRON/Delft (twinslot)
SRON/Delft (spiral)
SRON/Delft/MIT(HEB-QCL)
10hf/k
1000
HEB-QCL
100
0.4 0.50.60.70.8
0.91
J.J.A.Baselmans et al, Appl. Phys. Lett, 2004
M. Hajenius et al, Supercond. Sci. Technol, 2004
J.R. Gao et al, Appl. Phys. Lett, 2005
Z.Q. Yang et al, Supercond. Sci. Technol, 2006
M. Hajenius et al, ISSTT 2006, Paris
2
3
Frequency [THz]
4 5 6 78
Future space or balloon instruments
1)
2)
3)
4)
5)
TELIS ( German, Dutch, English), 500-650 GHz, 1.8 THz, 2.5 THz,
3.5THz (OH line)
Japanese BSMILE, 2.5 or 3.5 THz (OH line)
German-US, SOFIA 2.6, and 4.7 THz
Proposal: US Stratospheric THz Observatory (STO), 2.7 THz
Proposal: European ESPRIT ( 6 telescopes, heterodyne), 2-6 THz,
Space concept mission
Requirements of THz QCLs for future space or balloon
instruments
1)
2)
3)
Prefer to have operating temperature around 70 K If so, the input
power is a less important issue
Or 5-10 K, then the input power must be low, e.g. < 100 mW
QCL output power of 1.3 µW – 16 µW , corresponding to the power
at HEB (30 nW – 500 nW) If Gaussian beam
See Z.Q. Yang et al, IRMMW THz2005 paper
4)
A reasonable good beam, ideally a Gaussian beam
5)
DFB or other frequency control capability, at the target frequency
within 3-4 GHz. A bit tuning range will be very helpful
Phase or frequency locking, which depends on the application
6)
Z.Q. Yang, M. Hajenius, J.N. Hovenier, A. Baryshev, J.J.A. Baselmans, J.R. Gao, T.M. Klapwijk, A.J.L. Adam,
T.O. Klaassen, B.S. Williams, S. Kumar, Q. Hu and J. L. Reno, IRMMW-THz2005, Williamsburg, Virginia, USA,
Sep. 19-23, 2005, p465-466.
FTS spectral of THz QCL (a.u.)
Phase locking and linewidth of two-mode QCLs
3
Temp
5K
2.7 THz QCL
Spectrum analyzer
(two modes)
Source locking
microwave counter
2
7,700 GHz
HEB Mixer
1
2.7300 2.7360
coupler
IF Amp
MIT
group
0.1-12
GHz
phase
error signal
2.7420 2.7480 2.7540 2.7600
Frequency (THz)
40 µm
25
10 µm
•Metal-metal waveguide GaAs/AlGaAs QCL
THz Radiation
- 2.8 THz, has two lateral modes
- the difference in frequency ~ 7-8 GHz
-different temperature and current dependence
- Two modes are not strongly correlated
µm
670
1
mm
Active region
7.69999
7 .6 9 9 9 9
-20
(a)
RBW:1 kHz
0.8
0.30
7.70000
120 Hz
Beat signal power (a.u.)
0.28
7.70001
(b)
Beat signal power (dB)
Beat signal power (dB)
-10
0 .2 6
Bias Current (A)
-30
-40
1.1 kHz
7.6
0.26
-20
(a)
RBW:1 kHz
Cold plate T=7 K
7.8
RBW:100 Hz
-10
Beat Frequency (GHz)
Beat signal power (dB)
Results: phase locking and linewidth
Points: exp. data
line: Lorentzian fit
FWHM Linewidth:12.6 kHz
RBW;10 KHz
VBW;100 Hz
SWT;1 s
0.4
(b)
RBW:100 Hz
0.0
7.72390
-30
7.72400
Frequency (GHz)
7.72410
-40
7.699998
7.699998
-10
-20
7.700000
10 Hz
7.700002
(c )
(c)
R B W : 1 0 Hz
RBW:10
H z
-30
-40
-50
-60
7.6999998
•Realized phase-locking
• two Lorentzian, by “2” ⇒ 6.3 kHz
for single line
• Linewidth ΔνSchawlow-Townes = 0.7 KHz,
7.7000000
7.7000002
Frequency (GHz)
A. Baryshev, J.N. Hovenier, A.J.L. Adam, I. Kašalynas, J.R. Gao, T.O. Klaassen, B.S. Williams, S. Kumar, Q. Hu, and J. L.
Reno, Appl. Phys. Lett. 2006
Requirements of LO source for a lab test
•
•
•
Any THz frequenceis, but hope not in the strong water absorption
A directional and focus beam
Power of > 16 µW at QCL ( 500 nW at HEB, a big HEB)
or 1.3 µW if we use a small HEB (30 nW)
•
•
4 K to any temperatures
Input power , prefered to be 1 W or less
40% R.H.
60% R.H.
80 % R.H.
loss [dB/m]
100
10
1
2600
2800
3000 3200
Frequency[GHz]
3400
3600