|
HOME
All Fiber Doppler Velocity Interferometer Systems
a new kind of VISAR
new extremely pure laser
Series G
Unamplified
Single Photodetectors
for light levels
of 0.1 mW and higher
Series F Amplified
Single Photodetectors
with new improved amplifiers
for light levels down to nanowatts and below
Series J Amplified
Differential Photodetectors
like Series F single detectors,
but only the difference is amplified
Power Supply
recommended
for DC coupled PDMs
and all Differentials
International Order
Policies
|
|
Martin, Froeschner &
Associates
Series F Fast Compact Photodetector Modules
Newly Revised Amplifier Options
Even Higher Gain with Four Stages of Amplification in the same
Compact Module Size
Bandwidths to 12 GHz
Sensitivities to over thirty million V/W
And a new Ultra-Low Noise Series with Noise Figures as low as 0.9 dB
Faster, more compact, and cheaper
than our Award Winning Series 99 Photodetectors.
A new line of inexpensive and compact fiber-coupled photodiode
modules simplify capturing fast transient light signals for analysis. These
devices are intended to approximate as closely as possible, a length of fiber
optic cable that can be connected directly onto the input jacks of your
oscilloscope or other electronic data acquisition device. Conversion of the
optical signal to electronic current and voltage occurs at the last possible
moment, within a mm or so of the input jacks of your
scope. Co-ax cable and the problems of reflections, termination loads, phase
distortion and so forth are totally eliminated. The devices are extremely
compact and rugged, taking up about as much room as
a typical BNC terminator
These modules are available with a broad range of configurations, connector
and fibre options, photodiode and amplifier choices
as detailed below.
Dimensions: 0.65" (16mm) diameter by 1" to 1.7" (25 to 43
mm), excluding connectors and optical fiber
Construction: machined from solid 6061-T6 Aluminum, internal
components potted in epoxy resin
Power: shielded four-conductor cable to External Power Supply.
[Back to Top]
Optical
Fiber and Connector
We will build your modules with whatever optical fiber, cable and connectors
you specify. We normally stock single-mode 9/125 µm and both 50/125 µm and
62.5/125 µm multimode fiber with 0.9mm polymer buffer and 3mm Kevlar jacket.
Other types such as 100/140 µm are available. The fiber to photodiode
connection is angle polished for low (-45dB) back reflection.
The input end of the optical fiber will be fitted with whatever type of
optical fiber connector you desire. The range of normal options include:
none, i.e. a bare fiber pigtail, 2 mm ceramic ferrule only, NTT-FC, SC,
ST and SMA. The fiber end itself will be polished to any of the standard
specifications: flat, UPC, or APC (8o). If you need something
else, just specify so on the Order Form.
[Back to Top]
Optional Light Collecting Optics
If the signal you want to analyze is in the form of a beam in free-space we
can provide light collecting optics instead of or in addition to the optical
fiber connectors described above. A 6 mm diameter fixed focus aspheric lens
assembly is available. We also offer a micro-alignable
fixture with 27 mm aperture focusable achromatic lens. Precision fine thread
adjustments allow you to maximize the coupling of the incoming beam into the
fiber. The unit is also directly compatible with "micro-rail"
optical component systems made by Newport,
Melles-Griot, ThorLabs
and others and is "C" threaded for compatibility with Edmund
Scientific's modular component line. Finally, large aperture catadioptric systems for collecting light from weak,
distended or distant sources can be provided. Details available upon inquiry.
[Back to Top]
Photodiode Selection
 The two major
considerations in selecting the photodiode for your application are spectral
response and speed. Photodiodes based on different semiconductor materials
have, in general, different ranges of light wavelength to which they are most
sensitive.
For example, Silicon based diodes are most sensitive in the 400nm (nearly UV)
to 1000nm (near IR) spectral range and cover the visible well. InGaAs is relatively insensitive to visible light but
responds well to the IR used in information systems.
The intrinsic speed of the photodiode is also determined by the semiconductor
material. The higher electron mobility in InGaAs
allows response times which are simply not attainable with Si. Our latest
GaAs model offers unprecedented speed in the visible range. Other factors
which might be important to your needs, such as Dark Current and Capacitance
are also listed in the table on Photodiode Specifications. The maximum allowable input optical power
is 10 mW.
The photodiode in all our modules is reverse biased to minimize
intrinsic capacitance for maximally fast response.
[Back to Top]
Photodiode Specifications
Specifications are listed for the usual photodiodes. Others are available,
call or write for details.
|
|
GaAs
|
InGaAs-1
|
InGaAs-2
|
InGaAs-3
|
|
Spectral Range
|
450-870 nm
|
850-1700 nm
|
850-1700 nm
|
950-1650 nm
|
|
Responsivity
|
0.60 A/W at 850
|
0.9 A/W@1550
|
0.9 A/W@1550
|
0.9 A/W@1550
|
|
Bandwidth (-3db)
|
10 GHz
|
3.5 GHz
|
>7.5 GHz
|
>10 GHz
|
|
Rise/Fall Time
|
<35 ps
|
100 ps
|
<50 ps
|
<35 ps
|
|
Capacitance
|
0.2 pF
|
0.6 pF
|
0.17 pF
|
<0.2 pF
|
|
Active Area
|
75 µm dia.
|
100 µm dia.
|
50 µm dia.
|
30 µm dia.
|
|
Dark Current
|
<0.3 nA
|
<0.4 nA
|
<0.4 nA
|
<0.4 nA
|
|
Fiber Compatibility
|
up to 62.5 µm
|
up to 100 µm
|
up to 50 µm
|
single mode
|
[Back to Top]
Transimpedance
Amplifier Options and Specifications
When the light level gets below the mW regime, the
expected signal is uncomfortably near the noise floor of most systems. In
order to get acceptable signal levels from very low light levels the current
from the photodiode must be amplified. In the Series F modules we use the
latest microwave GaAs and InGaP technology in
Darlington configurations. This allows much higher performance than the
classical configuration using an Op-amp with feedback resistance. Expected signal levels can be estimated as
described below, Estimation of Signal
Level. Note that these amplifiers
are built into the Photodetector module body, closely coupled to the
photodiode and the electrical output for maximum performance. They are not a separate component.
We have recently completely revised our transimpedance
amplifier line, using components from new sources with higher bandwidth,
better gain flatness and lower noise figures than before. These new amplifier options are available,
as before, in single stage versions with true DC coupling, and in AC coupled multi-stage
configurations. We are also now
offering a new series with extremely low Noise specifications and very high
overall gain.
Other amplifier options are available.
Let us know what you need and we will do our best to devise a
configuration that meets your needs.
[Back to Top]
True DC
Coupling with Offset Null
These amplifiers work all the way down to zero Hertz, i.e. CW, and are useful
where the absolute value of light intensity must be measured as opposed to
mere variations in intensity. They use
two identical amplifiers, one driving the center conductor of the output
connector with the amplified photodiode signal, the other driving the outer
or ground conductor of the output with a DC signal to compensate for the DC
offset inherent with Darlington pair configured amplifiers. This DC Offset can be varied to null out
any background due to dark current or other sources. We recommend that our Power supply with
provision for this Offset Null feature be used with these amplifiers.
|
|
Bandwidth
(-3db)
|
Transimpedance
|
Gain Flatness
|
Noise
Figure, NF
|
Output Power (P1dB)
|
|
Mod 5D
|
DC to 12 GHz
|
200 volts/amp
|
±1.5 dB, 100 MHz to 12 GHz
|
4.9 dB @ 3 GHz
|
14.5 dBm
|
|
Mod 8D
|
DC to 7 GHz
|
300 volts/amp
|
±2 dB, 500 MHz to 5 GHz
|
3.2 dB @ 2 GHz
|
12.4 dBm
|
|
Mod 4D
|
DC to 2.8 GHz
|
2,500 volts/amp*
|
±0.8 dB, DC to 2 GHz
|
2.6 dB @ 1.5 GHz
|
-2 dBm
|
Note: The Transimpedance specification for Mod
4D amplifier given above assumes high impedance termination. Due to the relatively low output power of
this amplifier, the Transimpedance when terminated
into 50 ohms is approximately one-half of the specified value. This applies only to the Mod 4D amplifier,
all others will drive 50 ohm as well as high Z termination with no change in
specifications
.
[Back to Top]
Highest Performance, AC Coupled
We have recently greatly increased the amplification and overall
performance available in the AC coupled
Photodetector Modules. Advanced fabrication techniques now allow us to
package four stages of amplification in the same module body as before with
no increase in size. These new single
and multi-stage AC coupled transimpedance
amplifiers provide bandwidths up to 12 GHz, with excellent Gain
Flatness. Overall conversion gains over
10,000 volts/watt allow detection of sub micro-watt signals with bandwidths
still at nearly 6 GHz and above. For
lower Noise and even higher gain, see below.
|
|
Bandwidth (-3dB)
|
Transimpedance
|
Gain
Flatness
|
Noise Figure, NF
|
Output Power (P1dB)
|
|
Mod 5A
|
30 kHz to 12 GHz
|
200 volts/amp
|
±1.5 dB, 100 MHz to 12 GHz
|
4.9 dB @ 3 GHz
|
14.5 dBm
|
|
Mod55A
|
40 kHz to 8.4 GHz
|
750 volts/amp
|
±3 dB, 100 MHz to 8 GHz
|
5.7 dB @ 3 GHz
|
14.5 dBm
|
|
Mod 555A
|
50 kHz to 7 GHz
|
2,700 volts/amp
|
±4 dB, 100 MHz to 6 GHz
|
5.9 dB @ 3 GHz
|
14.5 dBm
|
|
Mod 5555A
|
60 kHz to 5.9 GHz
|
10,800 volts/amp
|
±5 dB, 100 MHz to 5 GHz
|
5.9 dB @ 3 GHz
|
14.5 dBm
|
[Back to Top]
Low Noise, High Gain, AC Coupled
These have been long-standing favorites. The Mod 4 series of single and multi-stage
AC coupled transimpedance amplifiers provide bandwidths
up to 2.8 GHz, with excellent Gain Flatness and low frequency response down
to 30 kHz. Overall conversion gains of
over a million volts/watt allow detection of sub micro-watt signals. For lower Noise and even higher gain, see
below.
|
|
Bandwidth (-3dB)
|
Transimpedance
|
Gain
Flatness
|
Noise Figure, NF
|
Output Power (P1dB)
|
|
Mod 4A
|
30 kHz to 2.8 GHz
|
2,500 volts/amp*
|
±0.8 dB, 50 MHz to 2 GHz
|
2.6 dB @ 1.5 GHz
|
-2 dBm
|
|
Mod42A
|
40 kHz to 2.8 GHz
|
7,500 volts/amp
|
±1.5 dB,50 MHz to 2 GHz
|
2.78 dB @ 1.5 GHz
|
12.4 dBm
|
|
Mod 442A
|
50 kHz to 2.0 GHz
|
200,000 volts/amp
|
±2 dB, 50 MHz to 2 GHz
|
2.68 dB @ 1.5 GHz
|
12.4 dBm
|
|
Mod 444A
|
50 kHz to 1.8 GHz
|
1,600,000 volts/amp*
|
±2 dB, 50 MHz to 2 GHz
|
2.68 dB @ 1.5 GHz
|
-2 dBm
|
[Back to Top]
Lower Noise,
Higher Gain, AC Coupled
We are introducing a new line of transimpedance
amplifier options to replace the venerable but obsolescent Mod 4 Series, for
those who need extremely low noise levels for detection of signals down in
the nano-watt regime. The principle difference between these and
the older Mod 4’s above are lower Noise Figure and Higher Gain at comparable
bandwidths, but with a somewhat higher low frequency cutoff.
|
|
Bandwidth (-3dB)
|
Transimpedance
|
Gain
Flatness
|
Noise Figure, NF
|
Output Power (P1dB)
|
|
Mod 9A
|
500 MHz to 5 GHz
|
600 volts/amp
|
±1.6 dB, 0.5 to 4.0 GHz
|
1.4 dB @ 1 GHz
|
20 dBm
|
|
Mod 99A
|
700 MHz to 3.5 GHz
|
7,400 volts/amp
|
±2 dB, 0.5 to 3.0 GHz
|
1.4 dB @ 1 GHz
|
20 dBm
|
|
Mod 999A
|
850 MHz to 2.9 GHz
|
90,000 volts/amp
|
±2 dB, 0.5 to 2.5 GHz
|
1.4 dB @ 1 GHz
|
20 dBm
|
|
Mod 9999A
|
1 GHz to 2.5 GHz
|
1,100,000 volts/amp
|
±2 dB, 0.5 to 2.5 GHz
|
1.4 dB @ 1 GHz
|
20 dBm
|
[Back to Top]
Ultra - Low Noise, Even Higher Gain, AC Coupled
And for those who need extremely low noise levels for
detection of signals down in the sub-nano-watt
regime, these amplifiers are available in four versions with Noise Figures below
1 dB, bandwidths as high as 2.2 GHz, excellent Gain Flatness and Transimpedance gains to over thirty million volts/watt
|
|
Bandwidth (-3dB)
|
Transimpedance
|
Gain
Flatness
|
Noise Figure, NF
|
Output Power (P1dB)
|
|
Mod 7A
|
20 MHz to 2.2 GHz
|
1,500 volts/amp
|
±1.5 dB, 0.4 to 1.8 GHz
|
0.9 dB @ 0.9 GHz
|
22 dBm
|
|
Mod 77A
|
30 MHz to 1.6 GHz
|
45,000 volts/amp
|
±2.5 dB, 0.4 to 1.4 GHz
|
0.9 dB @ 0.9 GHz
|
22 dBm
|
|
Mod 777A
|
35 MHz to 1.3 GHz
|
1,350,000 volts/amp
|
±3.5 dB, 0.4 to 1.0 GHz
|
0.9 dB @ 0.9 GHz
|
22 dBm
|
|
Mod 7777A
|
40 MHz to 1.0 GHz
|
40,000,000 volts/amp
|
±4.5 dB, 0.4 to 1.0 GHz
|
0.9 dB @ 0.9 GHz
|
22 dBm
|
[Back to Top]
Keep in mind that the transimpedance
amplifier is an option. If your light levels are adequate, use the basic
configuration Series G unamplified
(but biased) photodiode without the added current drain, cost and potential
additional noise of an amplifier.
We also make the Series J version
of all of these amplified modules, with dual optical inputs. In these Differential modules the two
photodiodes are arranged in a ‘totem-pole’ as in TTL logic. The amplifier
input is connected at the mid-point node between the two photodiodes and thus
sees only the difference between the two photodiode signals. Skip to the Series J page for details.
Series J Amplified Differential Photodetector
with Power Supply
Estimation of Signal Level
You can estimate the signal level (voltage) that you can expect to see, for
your light intensity, directly from the Responsivity as shown in the graph
above and the amplifier Transimpedance given in the
tables above, from:
V [volts] = I [watts] • Responsivity [amps/watt] • Transimpedance [volts/amp]
where V is the output signal, I is the
input light intensity.
Note that since the Responsivity of InGaAs is very
nearly 1, the Transimpedance figures can be thought
of directly as volts per watt of
optical input in systems with InGaAs photodiodes.
[Back to Top]
Noise Specifications and Measurements
Measurements of the noise spectrum have been made by independent labs on
several of our earlier systems. In all measurements the results were
consistent with or better than the published specifications.
An InGaAs-2 Mod1D with DC Offset Null contributed about 1.5mV rms over 20GHz with power on to both amplifiers and the
photodiode and no light input. (The scope by itself had an intrinsic noise
floor of about 1.2mV rms.) Calculations show this to be consistent with the
Noise Figure specified below. The equivalent optical noise density at the
input is about 50pW Hz -1/2. An AC coupled InGaAs-2 Mod2A system
tested at one of the National Laboratories showed a 0.3mV rms
noise floor, also consistent with the Noise Figure. The equivalent optical
input noise density is about 30pW Hz-1/2. This system reliably
receives digital data at 2.5Gb/s with light levels as low as a few microwatts.
Our latest amplifier models have even better Noise specifications, as well as
higher Gain, higher Bandwidth and improved Gain Flatness.
The noise from the photodiodes themselves is several orders of magnitude
below that of the amplifiers and may be ignored.
In general, we have found that the noise contributed by our amplified
photodiode systems is below or at most comparable to the intrinsic noise
floor of most high speed oscilloscopes and digital data acquisition systems. Our customers have told us that they are the
best they have ever seen.
[Back to Top]
Output Electrical Connector
Electronic output connector choices include BNC, TNC, SMA and SMC in either
gender. Wiltron-K, 7/16 and others are available at
some extra cost. Please note that BNC connectors are not recommended above 2
to 4 GHz. If you need something really unusual, specify on your Request for
Quotation or call to discuss your needs.
[Back to Top]
Input Coupling Option to Prevent Saturation
The photodiode is normally connected directly to the input terminal of the
first stage amplifier. In some
situations, such as the detection of a small signal riding on a large DC
component, the DC component might saturate the first stage amplifier. This can be avoided by capacitively
coupling the photodiode to the amplifier input, so that the DC component has
no effect. However, in this
configuration the photodiode must have a load resistor of about 50 ohms in
order to maintain its performance and since this parallels the amplifiers input
impedance, the overall transimpedance gain will be
reduced by roughly one-half.
To specify this Option, add another A to the Model number, for example, Mod
55AA.
[Back to Top]
Termination
These modules are designed to be mounted directly onto the input jack of your
scope. When used this way there is no coax cable to cause reflections so
terminating with exactly 50 ohms is not necessary. The output impedance of
the amplified modules is already low so you may set the input impedance of
your scope to 1Mohm. The amplifiers will drive a 50 ohm load but there may be
a reduction in signal level for certain amplifier configurations as explained
above.
[Back to Top]
Power Considerations
The amplified Series F modules are
powered through a shielded multi-conductor cable. This cable is fitted with a connector which
is compatible with the M,F&A Power Supply. Any power supply is a potential source of
noise. The M,F&A Power Supply provides noise free power to the photodiode
and amplifiers from Nickel metal hydride batteries which are re-charged when
the photodetector module is not in use. When the photodetector module is
active, the system is completely disconnected from the external AC source.
Amplified versions which are DC coupled would have an output
offset bias of several volts when the photodiode is dark, due to transistor
biasing. This offset is eliminated with the Offset Null configuration which
uses a second matched reference amplifier to drive the ground side of the
output connector. A multi-turn precision pot in the M,F&A Power Supply controls
the input to this second amplifier so that any residual offset due to
amplifier mismatch, photodiode dark current or background light can be
trimmed out.
The latest versions Mod5…, Mod 7… and Mod 9… can be powered by a simple 5v DC
Laboratory Grade Power Supply. Current
drain is about 150mA per stage. The
voltage should be well regulated and never exceed 6.0 volts.
[Back to Top]
Series F Amplified Photodetector
Module Summary and Prices
|
Input Optical Connector:
·
none
·
2.5mm ceramic ferrule
·
NTT-FC
·
SC
·
ST
·
SMA
·
other_______________
Polish:
·
UPC
(compatible with flat, PC, and SPC)
·
PC
·
APC 8 degrees
·
other ______________
Optical Cable:
·
9/125 µm
·
50/125 µm
·
62.5/125 µm
·
other______________
Jacket:
·
0.9mm buffer only
·
3mm Kevlar and Polymer over 0.9mm buffer
·
______________
Length:
·
1 meter (standard)
·
other_________________
Light-Collection Optics:
·
none
·
6mm fixed aspheric ($225)
·
alignable Micro-Rail and
"C" thread compatible ($695)
·
Large Aperture (inquire)
Photodiodes :
·
GaAs, 450-870nm, 10 GHz ($1,095)
·
InGaAs-1, 850-1700nm, 3.5 GHz ($895)
·
InGaAs-2, 850-1700nm, >7.5 GHz ($995)
·
InGaAs-3, 950-1650nm, >10 GHz ($1,095)
|
Amplifier Options:
True DC Coupling, with Offset Null
·
Mod 5D, 0 to 12 GHz, 200 ohms ($675)
·
Mod 8D, 0 to 7 GHz, 300 ohms ($675)
·
Mod 4D, 0 to 2.8GHz, 2,500 ohms ($775)
High Performance, AC Coupled
·
Mod 5A, 12 GHz, 200 ohms ($375)
·
Mod 55A, 8.4 GHz, 750 ohms($550)
·
Mod 555A, 7 GHz, 2,700 ohms ($725)
·
Mod 5555A,.5.9 GHz, 10,800 ohms ($900)
Low Noise, High Gain, AC Coupled
·
Mod 4A, 2.8 GHz, 2,500 ohms ($375)
·
Mod 42A, 2.8 GHZ, 7,500 ohms ($550)
·
Mod 442A, 2 GHz, 200,000 ohms($725)
·
Mod 444A, 1.8 GHz, 1,600,000 ohms ($725)
Lower Noise, Higher Gain, AC Coupled
·
Mod 9A, 5 GHz, 600 ohms ($475)
·
Mod 99A, 3.5 GHz, 7,400 ohms ($650)
·
Mod 999A, 2.9 GHz, 90,000 ohms ($825)
·
Mod 9999A, 2.5 GHz, 1,100,00 ohms ($1,000)
Ultra Low Noise, Higher Gain, AC
Coupled
·
Mod 7A, 2.2 GHz, 1,500 ohms ($475)
·
Mod 77A, 1.6 GHz, 45,000 ohms($650)
·
Mod 777A, 1.3 GHz, 1,350,000 ohms ($825)
·
Mod 7777A, 1.0 GHz, 40,000,000 ohms ($1,000)
Output Electronic Connector:
·
BNC
·
TNC
·
SMA
·
SMC
·
other________
·
Gender:
·
male plug (as in the photos above)
·
female jack
Input Coupling Option:
·
normal
·
capacitive, non-saturating (additional
A to Model Number)
Standard External Power Supply:
·
12volt rechargeable NiMH with EMI/RFI shielding ($375)
|
[Back to Top]
How to Order
We will build your Photodetectors to your specifications. The price of your
detector is simply the sum of the prices of the chosen specified options. Email us your specifications from the list
under Summary and Prices above. We will return a formal quotation to confirm
your specifications and expected delivery time. Quantity discounts are
available, send a Request for Quotation.
Please note that these modules contain technology at the leading
edge of the state of the art. Prices and specifications are subject to
change.
[Back to Top]
Martin,
Froeschner & Associates
14300 Mines Road, Livermore, California,
94550
USA
tel: (+1) 925 989 4930
fax: (+1) 925 449 4647
email:
sales@mfaoptics.com
Latest
update June 2016
©1999-2016
[Back to Top]
|
|
Contact Us:
tel: +1 925 989 4930
fax: +1 925 449 4647
email: sales@mfaoptics.com
Martin, Froeschner & Associates
14300 Mines Road
Livermore, California
94550
USA
Papers by Users of our FDVI
Upgrade your FDVI
to a New
Mark IV or Mark IV-3000
System
See us in the new
Physics Today Buyer's Guide
under
VISAR
and
Photodetectors
and
our
company profile.
See us in these Buyer’s Guides:
Global
Spec
Laser
Focus World
Photonics
Spectra
|
