I get an empty error when submitting multiple forms with file uploads with ajax in laravel

my problem is while posting multiple forms with ajax in laravel, I am sending the form data without any problem, but I cannot send the file.
File is empty error. I’ve been dealing with this for 2 days, there is no method I haven’t tried, please help me.
Apart from that, I added multipart to the form, but it still didn’t work, I’m sharing my codes with you.

Sorry for my bad english.

I want it to upload 2 photos in the normal 4th form until the createProduct3 form, I tried to get them by doing the normal new formData() and I tried otherwise and I couldn’t succeed.
It sends it to Laravel server side as [Object File].
My Form

<form class="form" id="createProduct4" method="POST" action="">
<input type="file" class="upload-box-title" id="urun-fotografi" name="urun_fotografi" value="Fotoğraf Seç">
<input type="file" class="upload-box-title" id="urun-dosyasi" name="urun_dosyasi" value="Dosya Seç">
</form>

My blade ajax:

function createProducts()
{
    var dataString = $("#createProduct1, #createProduct2, #createProduct3, #createProduct4").serialize();
    let photo = document.getElementById("urun-dosyasi").files[0];
    let photo2 = document.getElementById("urun-fotografi").files[0];
    console.log(photo,photo2);

    $.ajax({
        url: "{{ route('user.product.create') }}",
        type: "POST",
        data: dataString+"&urun_dosyasi="+photo+"&urun_fotografi="+photo2,
        success: function( data ) {
            $('#submit').html('Submit');
            $("#submit"). attr("disabled", false);
            Swal.fire({
                title: "Bilgi mesajı!",
                html: data,
                showConfirmButton: true
            })
        },
        error: function(xhr)
        {
            console.log(xhr);
            var err = JSON.parse(xhr.responseText);
            Swal.fire({
                title: "Hata!",
                html: err.message,
                icon: 'error',
                showConfirmButton: true
            })
        }
    });
}

Server Function

 public function createProduct(Request $request)
{
    $file = $request->file('urun_dosyasi');
    $file2 = $request->file('urun_fotografi');
    $filename = $file->getClientOriginalName();
    $extension = $file->getClientOriginalExtension();
    $filename2 = $file2->getClientOriginalName();
    $extension2 = $file2->getClientOriginalExtension();

    echo $filename,$extension."2. doc: ".$filename2.$extension;
}

Javascript error:

Screenshot a error image